Optical enhancing durable anti-reflective coating

ABSTRACT

Disclosed herein are polysilsesquioxane based anti-reflective coating (ARC) compositions, methods of preparation, and methods of deposition on a substrate. In embodiments, the polysilsesquioxane of this disclosure is prepared in a two-step process of acid catalyzed hydrolysis of organoalkoxysilane followed by addition of tetralkoxysilane that generates silicone polymers with &gt;40 mol % silanol based on Si-NMR. These high silanol siloxane polymers are stable and have a long shelf-life in the polar organic solvents at room temperature. Also disclosed are low refractive index ARC made from these compositions with and without additives such as porogens, templates, Si—OH condensation catalyst and/or nano-fillers. Also disclosed are methods and apparatus for applying coatings to flat substrates including substrate pre-treatment processes, coating processes including flow coating and roll coating, and coating curing processes including skin-curing using hot-air knives. Also disclosed are coating compositions and formulations for highly tunable, durable, highly abrasion-resistant functionalized anti-reflective coatings.

STATEMENT REGARDING GOVERNMENT FUNDING

This invention was made with government support under ContractDE-EE0006040 awarded by the U.S. Department of Energy. The governmenthas certain rights in the invention.

BACKGROUND OF THE DISCLOSURE

1. Field

The present disclosure relates to a soluble high silanol containingsilsesquioxane compositions having good solution stability, a method fortheir preparation, and a method of preparing thin-film coating using thesame.

2. Description of Related Art

A solar cell (PV), a light emitting diode (LED), an organic lightemitting diode (OLED) device, and other display devices have beenapplied in various fields, for example, residential electric devices,lighting devices, display devices, industrial buildings, automobiles andaerospace components. Transparent glass or plastic are used with theselight harvesting and light display devices which can reflect incidentlight and reduce the transmitting light, which reduces their efficiency.For example, PV module glass reflects more than 4% of sun light whichreduces the efficiency of the solar cell. However, existing approachesfor forming anti-reflective (AR) coatings have limitations in terms ofdurability, hydrophobicity and abrasion resistance.

A need remains for better AR coating on solar glass or modules thatenhances the photon transmission and improves hydrophobicity anddurability in harsh environmental conditions.

SUMMARY OF THE DISCLOSURE

An object of this disclosure is to provide a coating composition whereinthe cured film has high light transparency, low light reflection, goodmechanical properties, and sufficient weather resistance and durabilityto withstand prolonged outdoor exposure. Another object is to provide anarticle coated with said composition.

In one of its aspects, the disclosure provides a 2 step acid catalyzedprocess that results in a composition having the following formula A:[RSi(OH)₂O_(0.5)]_(a)[RSiO_(1.5)]_(b)[RSi(OH)O]_(c)[R′Si(OH)₂O_(0.5)]_(m)[R′Si(OH)O]_(p)[SiO₂]_(x)[Si(OH)O_(1.5)]_(y)[Si(OH)₂O]_(y)[Si(OH)₃O_(0.5)]_(z)

where R is independently methyl or optionally substituted orunsubstituted C2 to C10 alkyl group, a substituted or unsubstituted C3to C20 cycloalkyl group, a substituted or unsubstituted C1 to C10hydroxyalkyl group, a substituted or unsubstituted C6 to C20 aryl group,a substituted or unsubstituted C2 to C20 heteroaryl group, a substitutedor unsubstituted C2 to C10 alkenyl group, a substituted or unsubstitutedcarboxyl group, a substituted or unsubstituted (meth)acryl group asubstituted or unsubstituted glycidylether group, or a combinationthereof; R′ is a fluorine substituted C3 alkyl group or optionally C4 toC10 alkyl group, a fluorine substituted C3 to C20 cycloalkyl group, afluorine substituted C1 to C10 hydroxyalkyl group, a fluorinesubstituted aryl group, a fluorine substituted C2 to C20 heteroarylgroup, a fluorine substituted C2 to C10 alkenyl group, a fluorinesubstituted carboxyl group, a substituted or unsubstituted (meth)acrylgroup, a fluorine substituted glycidylether group, or a combinationthereof; and 0<a,b,c,x,y,z<0.9, 0≦m,n,p<0.9, and a+b+c+m+n+p+x+y+z=1.

In accordance with a second embodiment of the present disclosure, aprocess for the preparation of structure A composition is providedcomprising hydrolyzing at least one organotrialkoxy silane ortetraalkoxysilane in the presence of acid catalyst in a polar organicsolvent followed by reacting the resulting highly branched high silanolcontaining siloxane polymer with tetraalkoxy silane ororganotrialkoxysilane.

In accordance with a third embodiment of the present disclosure, a polarsolvent selected from alcohols, esters, ethers, aldehydes, and ketonessuch as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, ethyleneglycol, propylene glycol, ethyl acetate, ethylene glycol, formamide,dimethylformamide, N-methylpyrrolidinone, propylene glycol methyl ether,1-methoxy-2-propanol, propylene glycol, propylene glycolmethyletheracetate, acetone, cyclohexanone, methylethylkeone,N,N-dimethyl acetamide, dimethylether, diethylether, 2-butanol,2-butanone, tetrahydrofuran, 1,2-diethoxyethane, diethyleneglycol,triethyleneglycol, 1,2 dimethoxymethane and methyl t-butyl ether is usedin the formulation.

In accordance with a fourth embodiment of the present disclosure,additives such as adhesion promoters, surfactants, high boiling pointpolar porogens, templates, nano-fillers, and base condensation catalystsmay be used in the formulation.

In an aspect, a siloxane polymer solution composition may include asiloxane polymer A formed from acid hydrolyzed alkoxysilanes,organosilane, and organofluorosilane, wherein the hydrolyzedorganosilane and the hydrolyzed organofluorosilane are each separatelyprepared before combining with each other and with alkoxysilane or withanother reagent, wherein the siloxane polymer A has the followingformula:[RSi(OH)₂O_(0.5)]_(a)[RSiO_(1.5)]_(b)[RSi(OH)O]_(c)[R′Si(OH)₂O_(0.5)]_(m)[R′SiO_(1.5)]_(n)[R′Si(OH)O]_(p)[SiO₂]_(x)[Si(OH)O_(1.5)]_(y)[Si(OH)₂O]_(y)[Si(OH)₃O_(0.5)]_(z), where R is selected from the group consisting ofindependently methyl or optionally substituted or unsubstituted C2 toC10 alkyl group, a substituted or unsubstituted C3 to C20 cycloalkylgroup, a substituted or unsubstituted C1 to C10 hydroxyalkyl group, asubstituted or unsubstituted C6 to C20 aryl group, a substituted orunsubstituted C2 to C20 heteroaryl group, a substituted or unsubstitutedC2 to C10 alkenyl group, a substituted or unsubstituted carboxyl group,a substituted or unsubstituted (meth)acryl group a substituted orunsubstituted glycidylether group, or a combination thereof, R′ isselected from the group consisting of a fluorine substituted C3 alkylgroup or optionally C4 to C10 alkyl group, a fluorine substituted C3 toC20 cycloalkyl group, a fluorine substituted C1 to C10 hydroxyalkylgroup, a fluorine substituted aryl group, a fluorine substituted C2 toC20 heteroaryl group, a fluorine substituted C2 to C10 alkenyl group, afluorine substituted carboxyl group, a substituted or unsubstituted(meth)acryl group, a fluorine substituted glycidylether group, or acombination thereof, 0<a,b,c,x,y,z<0.9, 0≦m,n,p<0.9, anda+b+c+m+n+p+x+y+z=1, and at least one additive selected from the groupconsisting of: a hydrolysis acid catalyst, a polar organic solvent, aporogen or template, a nano-filler, an adhesion promoter, a Si—OHcondensation catalyst, and a surfactant. The siloxane polymer A may havea weight average Molecular weight (Mw) of 600 to 10,000 Daltons. Thesiloxane polymer A may be 0.1 to 10 weight percent of the total weightof the sol. The alkoxysilane may be tetramethoxysilane, the organosilanemay be methyltrimethoxysilane, and the organofluorosilane may betrifluoropropyltrimethoxysilane. The alkoxysilane may betetraethoxysilane, the organosilane may be methyltrimethoxysilane, andthe organofluorosilane may be trifluoropropyltrimethoxysilane. Thealkoxysilane may be tetramethoxysilane, the organosilane may bemethyltrimethoxysilane, and the organofluorosilane may be(tridecafluoro-1,1,2,2-tetrahydrooctyl)trimethoxysilane. Thealkoxysilane may be tetraethoxysilane, the organosilane may bemethyltrimethoxysilane, and the organofluorosilane may be(tridecafluoro-1,1,2,2-tetrahydrooctyl)trimethoxysilane. The siloxanepolymer A may have a relative weight percent ratio of saidtetraalkoxysilane to a total of said organosilane and saidorganofluorosilane of about 0.2 to about 2. The hydrolysis acid catalystmay be selected from the group consisting of hydrochloric acid, nitricacid, sulfuric acid, phosphoric acid, boric acid, methanesulfonic acidor acetic acid in amount of 0.01 to 1.0 weight present of the total solformulation. The polar organic solvent may be selected from the groupconsisting of alcohols, esters, ethers, aldehydes, and ketones; andwater, wherein an amount of the amount of said solvent and said water insaid mixture is from about 50% to about 99.5% by weight. The porogen ortemplate may be selected from the group consisting of ethylene oxide,propylene oxide, polyethylene oxides, polypropylene oxides, ethyleneoxide/propylene oxide block co-polymers, polyoxyethyltedpolyoxypropylated glycols, fatty acid ethoxylates, ethylene glycolesters, glycerol esters, mono-di-glycerides, glycerilesters,polyethylene glycolesters, polyglycerol esters, polyglyceryl esters,polyol monoesters, polypropylene glycol esters, polyoxyalkylene glycolesters, polyoxyalkylene propylene glycol esters, polyoxyalkylene polyolesters, polyoxyalkylene glyceride esters, polyoxyalkylene fatty acid,sorbitan esters, sorbitan fatty acid esters, sorbitan esters,polyoxyalkylene sorbitan esters, polyoxyethylene sorbitan monolurate,polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitantristearate, and sorbitan ester ethoxylates in an amount of 0.0 to 5 wt% of total sol composition. The nanofiller may be selected from thegroup consisting of colloidal silica, hollow silica nanospheres, polymerbeads, polylactic acid, polyvinylpyrrolidone, polymethylmethactrylatesand polyacrylates, carbon nanotubes, or Buckminsterfullerene C₆₀-C₇₀ inan amount of 0.0 to 5.0 wt % of the total sol formulation. The adhesionpromoter may be selected from the group consisting of(meth)acryloxypropyl trimethoxysilane, (meth)acryloxypropyltriethoxysilane, (meth)acryloxypropyl dimethylmethoxysilane,(meth)acryloxypropyl methyldimethoxysilane, 3-glycidopropyltrimethoxysilane, 3-glycidopropyl triethoxysilane, 3-glycidopropyldimethylmethoxysilane, or 3-glycidopropyl methyldimethoxysilane in anamount of 0.0-5.0 weight percent of the total sol formulation. The Si—OHcondensation catalyst may be selected from the group consisting ofalkali metal hydroxide, amide, amines, imidazolines, potassium hydroxide(KOH), sodium hydroxide (NaOH), cesium hydroxide (CsOH), ammoniumhydroxide (NH4OH), tetramethyl ammonium hydroxide (TMAH), formamide(FA), triethyl amine, trimethyl amine, formamide, dimethylformamide(DMF), N-methylpyrrolidinone (NMP), N,N-dimethyl acetamide (DMA),thermal base generator (TBG) or tetramethoxymethyl glycoluril(PowderLink 1174) in an amount of 0.0 to 1.0 wt % of the total solformulation. The surfactant may be selected from the group consisting ofnonionic surfactants, polyoxyethylene glycol alkyl ethers (Brij 58),polyoxyethylene octyl phenyl ether (TX-100), polyoxyethylene glycolsorbitan alkyl esters (polysorbate), ionic surfactants,cetyltrimethylammonium bromide and other tetraalkylammonium halides inan amount of 0.0 to 5.0 wt % of the total sol formulation. The siloxanepolymer may include 10 to 50 mol % Si—OH groups as established bySi-NMR.

In an aspect, a method of forming a coating on a glass substrate mayinclude preparing a siloxane polymer solution composition including asiloxane polymer A formed from acid hydrolyzed alkoxysilanes,organosilane, and organofluorosilane, wherein the hydrolyzedorganosilane and the hydrolyzed organofluorosilane are each separatelyprepared before combining with each other and with alkoxysilane or withanother reagent, wherein the siloxane polymer A has the followingformula:[RSi(OH)₂O_(0.5)]_(a)[RSiO_(1.5)]_(b)[RSi(OH)O]_(c)[R′Si(OH)₂O_(0.5)]_(m)[R′SiO_(1.5)]_(n)[R′Si(OH)O]_(p)[SiO₂]_(x)[Si(OH)O_(1.5)]_(y)[Si(OH)₂O]_(y)[Si(OH)₃O_(0.5)]_(z),where R is selected from the group consisting of independently methyl oroptionally substituted or unsubstituted C2 to C10 alkyl group, asubstituted or unsubstituted C3 to C20 cycloalkyl group, a substitutedor unsubstituted C1 to C10 hydroxyalkyl group, a substituted orunsubstituted C6 to C20 aryl group, a substituted or unsubstituted C2 toC20 heteroaryl group, a substituted or unsubstituted C2 to C10 alkenylgroup, a substituted or unsubstituted carboxyl group, a substituted orunsubstituted (meth)acryl group a substituted or unsubstitutedglycidylether group, or a combination thereof, R′ is selected from thegroup consisting of a fluorine substituted C3 alkyl group or optionallyC4 to C10 alkyl group, a fluorine substituted C3 to C20 cycloalkylgroup, a fluorine substituted C1 to C10 hydroxyalkyl group, a fluorinesubstituted aryl group, a fluorine substituted C2 to C20 heteroarylgroup, a fluorine substituted C2 to C10 alkenyl group, a fluorinesubstituted carboxyl group, a substituted or unsubstituted (meth)acrylgroup, a fluorine substituted glycidylether group, or a combinationthereof, 0<a,b,c,x,y,z<0.9, 0≦m,n,p<0.9, and a+b+c+m+n+p+x+y+z=1, and atleast one additive selected from the group consisting of: a hydrolysisacid catalyst, a polar organic solvent, a porogen or template, anano-filler, an adhesion promoter, a Si—OH condensation catalyst, and asurfactant; solution coating the solar glass or glass module with thesiloxane polymer solution, and curing the coating to form a thin film.The siloxane polymer solution may be prepared in a two-step processcomprising preparing hydrolyzed organosilane before combining with analkoxysilane. The siloxane polymer solution may be prepared in atwo-step process comprising preparing hydrolyzed alkoxysilane beforecombining with organosilane and fluorosilane. The siloxane polymersolution may be prepared in a two-step process comprising preparing thehydrolyzed alkoxysilane before combining with organosilane. The coatingmay be thermally cured at about 120° C. to about 700° C. The coating mayhave a thickness of about 80 nm to about 500 nm after curing. The glasssubstrate may be at least one of a window, an architectural glass, anLED, a semi-conductor, an exposed photovoltaic element, a lens, adiffuser, a mirror, a windshield, an automotive glass, a screen, adisplay, goggles, eyeglasses, sunglasses, a greenhouse glass, a hybridsolar surface, a marine glass, an aviation glass, a glass used intransportation, and a mobile device screen.

In an aspect, a coating may include a dried gel prepared from a siloxanepolymer A formed from acid hydrolyzed alkoxysilanes, organosilane, andorganofluorosilane, wherein the hydrolyzed organosilane and thehydrolyzed organofluorosilane are each separately prepared beforecombining with each other and with alkoxysilane or with another reagent,wherein the siloxane polymer A has the following formula:[RSi(OH)₂O_(0.5)]_(a)[RSiO_(1.5)]_(b)[RSi(OH)O]_(c)[R′Si(OH)₂O_(0.5)]_(m)[R′SiO_(1.5)]_(n)[R′Si(OH)O]_(p)[SiO₂]_(x)[Si(OH)O_(1.5)]_(y)[Si(OH)₂O]_(y)[Si(OH)₃O_(0.5)]_(z), where R is selected from the group consisting ofindependently methyl or optionally substituted or unsubstituted C2 toC10 alkyl group, a substituted or unsubstituted C3 to C20 cycloalkylgroup, a substituted or unsubstituted C1 to C10 hydroxyalkyl group, asubstituted or unsubstituted C6 to C20 aryl group, a substituted orunsubstituted C2 to C20 heteroaryl group, a substituted or unsubstitutedC2 to C10 alkenyl group, a substituted or unsubstituted carboxyl group,a substituted or unsubstituted (meth)acryl group a substituted orunsubstituted glycidylether group, or a combination thereof, R′ isselected from the group consisting of a fluorine substituted C3 alkylgroup or optionally C4 to C10 alkyl group, a fluorine substituted C3 toC20 cycloalkyl group, a fluorine substituted C1 to C10 hydroxyalkylgroup, a fluorine substituted aryl group, a fluorine substituted C2 toC20 heteroaryl group, a fluorine substituted C2 to C10 alkenyl group, afluorine substituted carboxyl group, a substituted or unsubstituted(meth)acryl group, a fluorine substituted glycidylether group, or acombination thereof, 0<a,b,c,x,y,z<0.9, 0≦m,n,p<0.9, anda+b+c+m+n+p+x+y+z=1; and at least one additive selected from the groupconsisting of: a hydrolysis acid catalyst, a polar organic solvent, aporogen or template, a nano-filler, an adhesion promoter, a Si—OHcondensation catalyst, and a surfactant. The coating may exhibit anabsolute reduction in reflection of about 1.0% to about 3.5% as comparedto uncoated glass, a thickness of about 80 to about 160 nm, andsufficient toughness, abrasion resistance, adhesion to glass to passstandard EN-1096-2 with an absolute change in reflection of no more than0.5% as measured after 2,000 abrasion strokes. The coating may improvethe peak power output of the solar module by about 1.0% to about 3.5% ona relative basis.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure and the following detailed description of certainembodiments thereof may be understood by reference to the followingfigures:

FIG. 1 a illustrates the UV-vis transmittance spectra comparing thetransmission gains of coating made from composition given in Example 2on tin vs non-tin side of float glass on a 30×30 cm substrate;

FIG. 1 b illustrates the UV-vis transmittance spectra of coating madefrom Example 3 roll coated on patterned glass substrate

FIG. 2 a illustrates the UV-vis transmittance spectra showing maximumtransmittance enhancement of coatings on tin side of TCO glasssubstrates made from compositions given in Example 3 with pre- andpost-abrasion spectra.

FIGS. 2 b and 2 c illustrates the UV-vis spectra of coatings on tin sideof TCO glass substrate made from composition of example 5 and 7respectively.

FIG. 3 a is TEM cross-sectional view of a coating made from thecomposition of Example 2 on a glass slide substrate;

FIG. 3 b is a High resolution TEM of a coating made from the compositionof Example 2 on a glass substrate;

FIG. 4 is an SEM cross-sectional view of a coating made from thecomposition of Example 2 on a 30×30 cm glass substrate;

FIG. 5 is an SEM cross-sectional view of a coating made from thecomposition of Example 3 on a 30×30 cm glass substrate;

FIG. 6 is an SEM cross-sectional view of a coating made from thecomposition of Example 4 on a 30×30 cm glass substrate;

FIG. 7 a-1 is a GPC of sol made from Example 2;

FIG. 7 a-2 showing the spread of the molecular weights for sol made fromExample 2;

FIG. 7 b-1 is a GPC of sol made from Example3;

FIG. 7 b-2 showing the spread of the molecular weights for sol made fromExample 3;

FIG. 7 c-1 is a GPC of sol made from Example 4;

FIG. 7 c-2 showing the spread of the molecular weights for sol made fromExample 4;

FIG. 7 d-1 is a GPC of sol made from Example 5;

FIG. 7 d-2 showing the spread of the molecular weights for sol made fromExample 5;

FIG. 7 e-1 is a GPC of sol made from Example 6;

FIG. 7 e-2 showing the spread of the molecular weights for sol made fromExample 6;

FIG. 7 f-1 is a GPC of sol made from Example 7;

FIG. 7 f-2 showing the spread of the molecular weights for sol made fromExample 7;

FIG. 7 g-1 is a GPC of sol made from Example 8;

FIG. 7 g-2 showing the spread of the molecular weights for sol made fromExample 8;

FIG. 7 h-1 is a GPC of sol made from Example 9;

FIG. 7 h-2 showing the spread of the molecular weights for sol made fromExample 9;

FIG. 7 k-1 is a GPC of sol made from Example 10;

FIG. 7 k-2 showing the spread of the molecular weights for sol made fromExample 10;

FIG. 8 a is the XPS spectrum of coating from Example 2 on tin side of TCof TCO coated glass; and

FIG. 8 b is the XPS spectrum of coating from Example 2 on tin side ofTCO coated glass after 10 minute Argon Sputter Etch.

FIG. 9 depicts an embodiment of flow coating;

FIG. 10 depicts a cross-sectional view of an embodiment of a flowcoating head;

FIG. 11 depicts a cross-sectional view of a second embodiment of a flowcoating head;

FIG. 12 depicts an isometric view of a flow coating head lower slotmanifold;

FIG. 13 depicts a partial view of the assembled flow coating head ofFIG. 10 and a corresponding substrate;

FIG. 14 shows a schematic cross-sectional view of a coating slotidentifying several critical dimensions and parameters;

FIGS. 15 a and 15 b depict a roll-coat system optimized for coating onflat substrates;

FIG. 16 depicts an embodiment of a roll-coat system for flat substrates;

FIG. 17 depicts an embodiment of a skin-cure system.

FIG. 18 depicts an example temperature profile for a skin-cure system.

FIG. 19 depicts an example of thermogravimetric analysis ofrepresentative samples of coating material.

FIGS. 20 a, 20 b and 20 c show data for an exemplary sol-gel coatingthat demonstrate control of final film thickness, refractive index andwater contact angle as a function of maximum cure temperature.

FIGS. 20 d and 20 e depicts an example of FT—IR analysis ofrepresentative samples of coating material before and after the curingprocess.

FIGS. 21 and 22 depicts Si-NMR spectra of example 2 and 3 respectively.

FIG. 23 is an SEM micrograph of the coated and cured sample of Example19 on float glass.

FIG. 24 is an SEM micrograph of the coated and cured sample of Example11 on rolled glass.

FIG. 25 is an SEM micrograph of the roll-coated and cured sample ofExample 11 on rolled glass.

FIG. 26 is a graph depicting the GPC-based shelf life of sol fromExample# 8 at 20° C.

FIG. 27 is a graph depicting the GPC-based shelf life of sol fromExample# 8 at 40° C.

FIGS. 28 and 29 depicts Si—NMR spectra of example 33 and 35respectively.

DETAILED DESCRIPTION

Various embodiments of the disclosure are described below in conjunctionwith the Figures; however, this description should not be viewed aslimiting the scope of the present disclosure. Rather, it should beconsidered as exemplary of various embodiments that fall within thescope of the present disclosure as defined by the claims. Further, itshould also be appreciated that references to “the disclosure” or “thepresent disclosure” should not be construed as meaning that thedescription is directed to only one embodiment or that every embodimentmust contain a given feature described in connection with a particularembodiment or described in connection with the use of such phrases. Infact, various embodiments with common and differing features aredescribed herein.

The present disclosure is generally directed to coatings that provide anoticeable improvement in anti-reflective properties. It is thecombination of the improved anti-reflective properties with theanti-soiling properties, self-cleaning properties and manufacturingflexibility as well as other benefits that further enhances the utilityof the coating. Accordingly, the coatings of the present disclosure maybe used on substrates, such as transparent substrates, to increase thelight transmittance through the substrates. In particular, the coatingsmay be used on transparent substrates such as glass or the front coverglass of solar modules.

Throughout this disclosure, solar modules are used as the exemplaryembodiment, but it should be understood that any optical element may beutilized with the system and methods described herein, such as windows,architectural glass, LEDs, semi-conductors, exposed photovoltaicelements, lenses, diffusers, mirrors, windshields, automotive glass,screens/displays, goggles, eyeglasses, sunglasses, greenhouse glass,hybrid solar surfaces, marine glass, aviation glass, glass used intransportation, mobile device screen, and the like.

The present disclosure is particularly well suited for use with glassused in solar energy generation (“solar glass”). It should be understoodthat solar energy generation includes solar photovoltaic and solarthermal, wherein solar insolation is used to produce heat either as anend-point or as an intermediate step to generate electricity.Furthermore it should be understood that solar glass may be used in anyapplication where maximal transmission of solar energy through the glassis desired such as for example in greenhouses or building environmentswhere warm temperatures are desired. Typically solar glass is hightransmission low iron glass. It may be either float glass, that is, flatglass sheets formed on a molten tin bath or patterned glass wherein theflat glass is formed by the action of rollers. Float glass is oftencharacterized by the presence of tin contamination on the bottom (“tinside”) of the glass. Patterned glass is typically textured on one sideto improve its performance in solar modules. It may also be formed intotubes such as those used as receivers in solar thermal energy generationor in some non-planar forms of solar photovoltaic generation.Embodiments of the present disclosure may also be applied to glasssurfaces used as mirrors in solar energy generation such as parabolictrough systems or in heliostats. It may also be used to coat variousglass lenses such as Fresnel lenses used in solar thermal generation.

Additionally, solar glass may have various coatings applied. For examplea common coating is a transparent conductive oxide (TCO) such asfluorine doped tin oxide (FTO) or indium tin oxide (ITO) on one side ofthe glass. This coating is used to provide the front electrode for manythin film solar module technologies. Other coatings may be present suchas coatings to seal in alkali ions such as Na+ and Ca+ that are used inthe manufacturer of the glass but that cause long term reliabilityproblems when leached out by water. Other techniques to solve thisproblem are to deplete these ions in thin layers of the glass surface.Solar glass may also be coated with a reflective surface to form amirror. Solar glass may be tempered, annealed or un-tempered. Temperedglass is significantly stronger and solar modules manufactured using ittypically only use one sheet of glass. If very thin tempered glass isused, then a second thin sheet of glass may be used as a back sheet forthe solar module. Solar modules manufactured with un-tempered frontglass typically use a back sheet of tempered glass to meet strength andsafety requirements. Many thin-film solar photovoltaic technologies alsouse the front glass as a substrate upon which they deposit materialsthat comprise the solar cell. The processes used during the manufacturerof the solar cell may adversely affect the properties of any existingcoatings on the glass or existing coatings may interfere with the solarcell manufacturing process. Embodiments of the present disclosure arecompletely tolerant of type of glass selected by the solar modulemanufacturer. It works well on float or patterned glass.

One critical issue for solar module manufacturers that use TCO (orsimilar) coated glass is tempering. It is very difficult to achievelow-cost, high quality TCO coated tempered glass. Therefore solar modulemanufacturers that requite TCO coated glass use untempered glass.Additionally even if suitable TCO coated tempered glass was availablesome thin-film solar manufacturing processes heat the glass duringmanufacturer to the extent that the temper is lost. Much of theanti-reflective coated glass on the market is tempered. Tempering is theprocess by which the glass is heated to 600° C. to 700° C., then quicklycooled. This high tempering temperature sinters the anti-reflectivecoating providing it with its final mechanical strength. Thus solarmodule manufacturers that cannot use tempered glass typically cannot useanti-reflective coated glass. In addition, some module manufacturers,especially thin film module manufacturers who might need to applyanti-reflective coatings on finished or substantially finished modulesare unable to use currently available anti-reflective coatings becausethe coating materials need to be cured at temperatures greater than 300°C. or exposed to a corrosive ammonia atmosphere or exposed to highlytoxic acids like hydrofluoric acid. Exposing finished or substantiallyfinished solar modules to temperatures >300° C. or exposing them to acorrosive ammonia atmosphere is likely to damage their performanceand/or long term reliability. Exposing finished modules to acids orother strong etchants to create a graded refractive index layer isequally challenging and poses an additional safety risk due to managingand disposing large quantities of a highly dangerous chemical likehydrofluoric acid. One of the embodiments of the disclosure may beapplied and cured at a low temperature of between 20° C. and 300° C. andbetween 20° C. and 130° C. and further between 80° C. and 250° C. Thislow temperature facilitates the coating of completed solar panelswithout damage to the panel. Thus it is an anti-reflective solution forusers of un-tempered solar glass and for users of anti-reflectivecoatings on finished or substantially finished solar modules.

The low temperature curing of one of the embodiments of the disclosurealso provides substantial benefits to solar module manufacturers beyondenabling un-tempered anti-reflective glass. By making possible thecoating of the glass without the need for the tempering step, solarmodule manufacturers are enabled to apply their own anti-reflectivecoating. Currently the requirement for a large tempering oven means thatsolar modules manufacturers are restricted to buying anti-reflectiveglass from glass manufacturers. This means that they must maintaininventory of both anti-reflective coated and non-coated glass. As thesecannot be used interchangeably inventory flexibility is reducednecessitating keeping larger amounts of inventory on hand. The abilityfor the solar module manufacturer to apply their own coating means thatthey can just hold a smaller inventory of non-coated glass and thenapply the anti-reflective coating to that as needed.

In addition, conventional anti-reflective coatings are prone toscratching during the solar module manufacturing process. Typicallysolar module manufacturers must use a plastic or paper sheet to protectthe coating. As the coatings disclosed herein can be applied to fullymanufactured solar modules, it can be applied at the end of themanufacturing process thus removing the need for the protection sheetand the opportunity for damage to the coating during manufacture.

Conventional anti-reflective coatings from different manufacturers tendto have subtle color, texture and optical differences. This presentsproblems to solar module manufacturers who desire their products to havea completely consistent cosmetic finish. If they manufacture largenumbers of solar modules it is almost inevitable that they will have toorder anti-reflective glass from different suppliers causing slightdifferences in the appearance of the final products. However, thecoatings disclosed herein enable solar module manufacturers to applytheir own coating and so enables cosmetic consistency over an unlimitednumber of solar modules.

For anti-reflective coatings on solar modules, it would also beimportant to tune and optimize the thickness of the antireflectivecoating on glass depending upon the type of solar cell that is used by asolar module manufacturer. This is because the spectral responses forcrystalline silicon, amorphous silicon, CdTe, CIGS, and other solar cellabsorber materials have slight differences and it would be beneficialfor the thickness of an antireflective coating to be optimized such thatthe maximum transmission for the antireflective coating occurs atwavelengths that are well matched to that of the underlying solar cellmaterial.

In addition, to their anti-reflective properties, the coatings describedherein can exhibit anti-soiling and/or self-cleaning properties, as theyare resistant to the adhesion of dirt and promote the removal of anyadhered dirt by the action of water. More specifically, some embodimentsof the coatings described herein can be characterized by extremely fineporosity that minimizes the deposition of dirt by physical means.Further, some embodiments of the coatings are characterized by a lowenergy surface that resists chemical and physical interactions and makesit easy to dislodge the particles, thereby making the surfacesessentially anti-soiling. The reduced physical and/or chemicalinteractions with the environment, such as dirt, make the exposedsurface of these coating less susceptible to binding of dirt and alsomake it easier to clean with a minimal expenditure of force or energy.

Typically in order to completely clean ordinary glass a mechanicalaction for example using brushes or high-pressure jets is required todislodge dirt that is strongly adhered to the surface. However someembodiments of the coatings described herein present a surface such thatdirt is more attracted to water then to the surface. Thus in thepresence of water any dirt resting on the surface is efficiently removedwithout the need for mechanical action. This means that coated glass mayachieve a high level of cleanliness in the presence of natural orartificial rain without human or mechanical intervention. In addition,the amount of water required to clean the glass is reduced. This is ofspecial significance given that the most effective locations for solarenergy generation tend to be sunny warm and arid. Thus water is aparticularly expensive and scarce resource in the very locations thatsolar energy is most effective.

Embodiments of the disclosure enable a reduction in the Levelized Costof Energy (LCOE) to the operator of a solar energy generating system.First, the anti-reflective property increases the efficiency of thesolar modules. Increased efficiency enables a reduction of cost in theBalance of System (BOS) costs in construction of the solar energygeneration system. Thus for a given size of system the capital costs andconstruction labor costs are lower. Second, the anti-soiling propertyincreases the energy output of the solar modules by reducing the lossesdue to soiling. Third the Operating and Maintenance (O&M) costs arereduced because fewer or no washings are needed reducing labor and watercost associated with washing.

In some embodiments described herein the coating can also contain waterand oil resistant hydro/fluoro-carbon groups that make them chemicallyless reactive and less interacting. When used in combination with aglass substrate, the coatings bind to the glass surface using siloxanelinkages that make them adhere strongly and makes them strong, durable,and abrasion and scratch resistant. These coatings are physically andchemically less reactive, mechanically and structurally stable,hydrophobic, oleophobic, stable, resistant to degradation by solarultra-violet (UV) light. Accordingly, it should be appreciated that thecoatings described herein have particular application to transparentsubstrates that are exposed to the environment, such as exterior windowsand glass used by solar modules.

Generally, the coatings described herein are prepared by a sol-gelprocess. The starting composition, referred to as a “coating mixture” or“coating composition,” includes a hydrolysate of organotrialkoxysilaneor a combination of organoalkoxysilanes and tetraalkoxysilane in a formof a homogenous gel-free solution of sol. This sol can be coated onto asubstrate using coating techniques known in the art, dried to form agel, and cured to form a hard layer or coating having the propertiesnoted above. The process of curing the dried gel further densifies thecoating.

Generally, the resulting properties of the coating described above areprovided by using a particular combination of components in theformation of the final coating. In particular, the selection of aparticular organoalkoxysilane precursor or mixture of organoalkoxysilaneprecursors in combination with other components in the coating mixtureis important in providing a coating with the desired properties. Forexample, in some embodiments, the coatings are made from a mixture oforganoalkoxysilane precursors including tetraalkoxysilane,organoalalkoxysilane, and fluorine-containing organoalkoxysilanes. Insome embodiments, separate coating mixtures or mixtures oforganoalkoxysilane precursors can be used to form separate sols that maythen be combined to form a final sol that is applied to a substrate tobe coated. Further, a single sol, or separately prepared sols that arecombined together, may be combined with another organoalkoxysilaneprecursor to form a final sol that is applied to a substrate to becoated.

For example, acid-catalyzed hydrolysis of tetraalkoxysilane form anextensively cross-linked structure due to the formation of four Si—O—Silinkages around each silicon atom. These structures are characterized bymechanical stability and abrasion resistance. To impart hydrophobicityand anti-soiling to the ultimate coating, organoalkoxysilanes (such asmethyltrimethoxysilane) can be used in addition to thetetraalkoxysilane. Further, to impart oleophobicity and anti-soilingcharacteristics, fluorine-containing organoalkoxysilanescan be used inaddition to the tetralkoxysilane.

It should be appreciated that the coating material and process by whichit is applied to the substrate can comprise a larger coating system. Thecoating material is optimized for a particular coating method and viceversa. Thus the optimized coating process is performed by a tooloptimized to insure consistency and quality. Therefore this tool coupledwith the coating materials comprises the coating system. Given that thebenefits of the current disclosure are particularly well suited to solarmodule manufacturers, who do not themselves manufacture tools; it isdesirable to offer a complete solution consisting of the coatingmaterial, the coating process knowledge and the associated coating tool.In the following paragraphs describing the coating process it should beappreciated that these steps could be executed manually, automaticallyusing a coating tool or in any combination of both. It should also beappreciated that there are several possible coating systems whereindifferent coating materials, coating processes and coating tools areused in combination.

The tool may be a large stand-alone unit intended for operation in afactory setting; it could be a sub-tool, such that it comprises aprocess module that performs the coating process but that is integratedinto another machine that performs other steps in the larger solarmodule manufacturing process. For example it could be a module attachedto an existing glass washing machine or a module attached to a solarmodule assembly machine. Alternatively, the tool could be portable orsemi-portable for example mounted on a truck or inside a tractor trailersuch that it could be transported to a worksite and used to coat solarmodules during the construction of a large solar installation.Alternatively it could be designed such that the coating could beapplied to installed solar modules in situ.

In general, three steps are used to apply the sol to a given substrate.First, the substrate is cleaned and pretreated. Second, the substrate iscoated with the sol or mixture of sols. Third, the final coating isformed on the substrate.

As an initial step, the substrate is pretreated or pre-cleaned to removesurface impurities and to activate the surface by generating a freshsurface or new binding sites on the surface.

It is desirable to increase the surface energy of the substrate throughpretreatment or cleaning of the substrate surface to form an “activated”surface. For example an activated surface may be one with many exposedSi—OH moieties. An activated surface reduces the contact angle the soland enables effective wetting of the sol on the surface. In someembodiments, a combination of physical polishing or cleaning and/orchemical etching is sufficient to provide even wetting of the sol. Incases, where the surface tension would need to be further lowered, thesubstrate, such as glass, may be pretreated with a dilute surfactantsolution (low molecular weight surfactants such as surfynol; long chainalcohols such as hexanol or octanol; low molecular weight ethylene oxideor propylene oxide; or a commercial dishwasher detergent such asCASCADE, FINISH, or ELECTRASOL to further help the sol spread better onthe glass surface.

Accordingly, surface pretreatment can involve a combination of chemicaland physical treatment of the surface. The chemical treatment steps caninclude (1) cleaning the surface with a solvent or combination ofsolvents, detergents, mild bases like sodium carbonate or ammoniumcarbonate and/or (2) cleaning the surface with a solvent along with anabrasive pad, (3) optionally chemically etching the surface, and/or (4)washing the surface with water. The physical treatment steps can include(1) cleaning the surface with a solvent or combination of solvents, (2)cleaning the surface with a solvent along with particulate abrasives,and (3) washing the surface with water. It should be appreciated that asubstrate can be pretreated by using only the chemical treatment stepsor only the physical treatment steps. Alternatively, both chemical andphysical treatment steps could be used in any combination. It should befurther appreciated that the physical cleaning action of frictionbetween a cleaning brush or pad and the surface is an important aspectof the surface preparation.

In the first chemical treatment step, the surface is treated with asolvent or combination of solvents with variable hydrophobicity. Typicalsolvents used are water, ethanol, isopropanol, acetone, and methyl ethylketone. A commercial glass cleaner (e.g., WINDEX) can also be employedfor this purposes. The surface may be treated with an individual solventseparately or by using a mixture of solvents. In the second step, anabrasive pad (e.g., SCOTCHBRITE) is rubbed over the surface with the useof a solvent, noting that this may be performed in conjunction with thefirst step or separately after the first step. In the last step, thesurface is washed or rinsed with water.

One example of substrate preparation by this method involves cleaningthe surface with an organic solvent such as ethanol, isopropanol, oracetone to remove organic surface impurities, dirt, dust, and/or grease(with or without an abrasive pad) followed by cleaning the surface withwater. Another example involves cleaning the surface with methyl ethylketone (with or without an abrasive pad) followed by washing the surfacewith water. Another example is based on using a 1:1 mixture of ethanoland acetone to remove organic impurities followed by washing the surfacewith water.

In some instances an additional, optional step of chemically etching thesurface by means of concentrated nitric acid, sulfuric acid, or piranhasolution (1:1 mixture of 96% sulfuric acid and 30% H₂O₂) may benecessary to make the surface suitable for bonding to the deposited sol.Typically this step would be performed prior the last step of rinsingthe surface with water. In one embodiment, the substrate may be placedin piranha solution for 20 minutes followed by soaking in deionizedwater for 5 minutes. The substrate may then be transferred to anothercontainer holding fresh deionized water and soaked for another 5minutes. Finally, the substrate is rinsed with deionized water andair-dried.

The substrate may alternatively or additionally prepared by physicaltreatment. In the physical treatment case, for one embodiment thesurface is simply cleaned with a solvent and the mechanical action of acleaning brush or pad, optionally a surfactant or detergent can be addedto the solvent, after which the substrate is rinsed with water and airdried. In another embodiment the surface is first cleaned with waterfollowed by addition of powdered abrasive particles such as ceria,titania, zirconia, alumina, aluminum silicate, silica, magnesiumhydroxide, aluminum hydroxide particles, silicon carbide, orcombinations thereof onto the surface of the substrate to form a slurryor paste on the surface. The abrasive media can be in the form a powderor it can be in the form of slurry, dispersion, suspension, emulsion, orpaste. The particle size of the abrasives can vary from 0.1 to 10microns and in some embodiments from 1 to 5 microns. The substrate maybe polished with the abrasive slurry via rubbing with a pad (e.g., aSCOTCHBRITE pad), a cloth, a foam, or paper pad. Alternatively, thesubstrate may be polished by placement on the rotating disc of apolisher followed by application of abrasive slurry on the surface andrubbing with a pad as the substrate rotates on the disc. Anotheralternative method involves use of an electric polisher that can be usedas a rubbing pad in combination with abrasive slurry to polish thesurface. The substrates polished with the slurry are cleaned by waterand air-dried.

After pretreating the surface, the coating is deposited on a substrateby techniques known in the art, including dip coating, spray, droprolling, flow coating or roll coating to form a uniform coating on thesubstrate. Other methods for deposition that can be used includespin-coating; aerosol deposition; ultrasound, heat, or electricaldeposition means; micro-deposition techniques such as ink-jet, spay-jet,xerography; or commercial printing techniques such as silk printing, dotmatrix printing, etc. Deposition of the sol is may be done under ambientconditions or under controlled temperature and humidity conditions. Insome embodiments the temperature is controlled between 20° C. and 35° C.and/or the relative humidity is controlled between 20% and 60% or morepreferably between 25% and 35%.

In some embodiments, the method of deposition is performed via the droprolling method on small surfaces wherein the sol composition is placedonto the surface of a substrate followed by tilting the substrate toenable the liquid to roll across the entire surface. For largersurfaces, the sol may be deposited by flow coating wherein the sol isdispensed from a single nozzle onto a moving substrate at a rate suchthat the flowing sol leads to a uniform deposition onto a surface orfrom multiple nozzles onto a stationary surface or from a slot onto astationary surface. Flow coating is described in greater detailelsewhere herein. Another method of deposition is via depositing theliquid sol onto a substrate followed by use of a mechanical dispersantto spread the liquid evenly onto a substrate. For example, a squeegee orother mechanical device having a sharp, well-defined, uniform edge maybe used to spread the sol such as roll coating which is described ingreater detail herein.

In addition to the actual methods or techniques used to deposit thefinal sol on the substrate, several variations for depositing the finalsol exist. For example, in some embodiments, the final sol is simplydeposited on the substrate in one layer. In other embodiments, a singlesol or multiple sols may be deposited to form multiple layers, therebyultimately forming a multilayered coating. For example, a coating of thesol containing high silanol terminal group can be formed as anunderlayer for better adhesion to glass substrate followed by a topcoatof a tetraalkoxysilane to obtain better abrasion resistance for theouter surface. In another embodiment, an underlayer of an organosilanemay be deposited followed by the deposition of a topcoat of a mixture ofan organofluoroalkoxysilane and a tetraalkoxysilane. In anotherembodiment, an underlayer of a tetraalkoxysilane may be depositedfollowed by the deposition of a top layer using a sol mixture of anorganoalkoxysilane and an organofluoroalkoxysilane. In anotherembodiment, an underlayer of a sol made from a mixture of anorganoalkoxysilane and an organofluoroalkoxysilane may be depositedfollowed by vapor deposition of a top layer by exposing the layer tovapors of a tetraalkoxysilane. In another embodiment, an underlayer of asol made from a mixture of an organoalkoxysilane and anorganofluoroalkoxysilane may be deposited followed by deposition of atop layer by immersing the substrate in a solution of atetraalkoxysilane in isopropanol. In the embodiments in which multiplelayers are deposited, each layer may be deposited shortly afterdeposition of the first layer, for example, within or after 30 secondsof deposition of the prior layer. As noted, different sols may bedeposited on top of one another, or different mixtures of sols may bedeposited on top of one another. Alternatively, a single sol may bedeposited in multiple layers or the same sol mixture may be deposited inmultiple layers. Further, a given sol may be deposited as one layer anda different sol mixture may be used as another layers. Further, anycombination of sols may be deposited in any order, thereby constructinga variety of multi-layered coatings. Further, it should be appreciatedthat the sols for each layer may be deposited using different techniquesif so desired.

The thickness of the coatings deposited can vary from about 10 nm toabout 5 μm. In some embodiments, the thickness of the coating variesfrom about 100 nm to about 1 micron, and in other embodiments it variesfrom about 100 nm to about 500 nm. In order to provide sufficientanti-reflective properties, a thickness of about 60 nm to about 150 nmis desired. The thickness of the coating mixture as deposited isaffected by the coating method, as well as by the viscosity of thecoating mixture. Accordingly, the coating method should be selected sothat the desired coating thickness is achieved for any given coatingmixture. Further, in those embodiments, in which multiple layers of solsare deposited, each layer should be deposited in a thickness such thatthe total thickness of the coating is appropriate to achieve the finaldesired transmission spectrum properties. Accordingly, in someembodiments in which multiple layers of sols are deposited, the overallcoating thickness varies from about 100 nm to about 500 nm, and in orderto provide sufficient anti-reflective properties, a total coatingthickness of about 60 nm to about 150 nm is desired.

Once the final sol is deposited as described above, the deposited solwill dry to form a gel through the process of gelation after which thegel is cured further to remove residual solvent and facilitate furthercondensation of Si—OH and network formation via Si—O—Si linkageformation in the coating. In addition, the gel may be allowed to age toallow for the formation of additional linkages throughcontinued—condensation reactions.

As described above, the sol-gel method used in preparing the coatingsdescribed herein utilizes a suitable molecular precursor that is acidhydrolyzed to generate a siloxane oligomers. Initial hydrolysis andpartial condensation of the precursor monomers generates a liquid sol,which ultimately turns to a solid gel during drying. Drying of the gelsunder ambient conditions (or at elevated temperature) leads toevaporation of the solvent phase to form a cross-linked film.Accordingly, throughout the process, the coatingmixture/sol/gel/dried/cured coating undergoes changes in physical,chemical, and structural parameters that intrinsically alter thematerial properties of the final coating. In general, the changesthroughout the sol-gel transformation can be loosely divided into threeinterdependent aspects of physical, chemical, and structural changesthat result in altered structural composition, morphology, andmicrostructure. The chemical composition, physical state, and overallmolecular structure of the sol and the gel are significantly differentsuch that the materials in the two states are intrinsically distinct.

Regarding physical differences, the sol is a collection ofsilanol-containing polysilsesquioxane oligomers (low Mw polymer)dissolved in a polar solvent. These silanol-containingpolysilsesquioxane oligomers are dissolved in a solvent and do notinteract with each other significantly. As such, the sol is stable andexists as a low viscosity transparent colorless liquid. In contrast, ina gel film the network formation has occurred to an advanced state suchthe siloxane polymers are interconnected to each other. The increasednetwork formation and cross-linking makes the gel network rigid with acharacteristic solid state. The ability of the material to exist in twodifferent states is because of the chemical changes (condensation ofSi—OH) that occur along the sol to gel transformation.

Regarding chemical changes, during the sol to gel transition, the solmolecules combine with each other via Si—OH condensation and formationof Si—O—Si linkages. As a result, the material exhibits networkformation and strengthening. Overall, the sol contain reactive Si—OHsilanol groups that can participate in formation of an Si—O—Si networkwhile the gel structure has some of these Si—OH silanol groups convertedinto Si—O—Si groups.

Regarding structural differences, the sol contains few Si—O—Si linkagesalong with terminal Si—OH silanol as well as unhydrolyzed alkoxyligands. As such, the sol state can be considered structurally differentfrom the solidified films, which contain more Si—O—Si linkages and fewersilanols. As such, the liquid sol and the solid state polymeric networksare chemically and structurally distinct systems.

Some combination of organoalkoxysilane precursors could provide a solwith a long shelf-life, while some combination of organoalkoxysilaneprecursors could provide a sol that could gel into a coating withsuperior abrasion resistance, while some other combination oforganoalkoxysilane precursors could gel into a coating with abrasionresistance and anti-soiling properties. Regarding differences inproperties, the origin of the physical and chemical properties of thesol and gel films depends upon their structure. The sol solution and thegel films differ in the chemical composition, makeup and functionalgroups and as a result exhibit different physical and chemicalproperties. The sol stage because of its particulate nature ischaracterized by high reactivity to form the network while the gel stateis largely unreactive due to conversion of reactive Si—OH silanol groupsto stable Si—O—Si linkages. Accordingly, it is the particularcombination of organoalkoxysilane precursors and other chemicals addedto the coating mixture that is hydrolyzed and condensed, gelled, driedand cured on a substrate surface that gives the final coatings of thepresent disclosure the desired properties described above.

In another embodiment, a combination of organoalkoxysilane andtetraalkoxysilane precursors with nanofillers such as colloidal silica(NALCO, NISSAN, EVONIK, LUDOX, BAXTER, CLARIANT) carbon nanotubes,Buckminsterfullerene C₆₀ and C₇₀ could provide a sol with a longshelf-life, and superior optical and mechanical performance.

High boiling point porogens selected from the group consisting ofethylene oxide, propylene oxide, polyethylene oxides, polypropyleneoxides, ethylene oxide/propylene oxide block co-polymers,polyoxyethylted polyoxypropylated glycols, fatty acid ethoxylates,ethylene glycol esters, glycerol esters, mono-di-glycerides,glycerilesters, polyethylene glycolesters, polyglycerol esters,polyglyceryl esters, polyol monoesters, polypropylene glycol esters,polyoxyalkylene glycol esters, polyoxyalkylene propylene glycol esters,polyoxyalkylene polyol esters, polyoxyalkylene glyceride esters,polyoxyalkylene fatty acid, sorbitan esters, sorbitan fatty acid esters,sorbitan esters, polyoxyalkylene sorbitan esters, polyoxyethylensorbitan monolurate, polyoxyethylene sorbitan monostearate,polyoxyethylene sorbitan tristearate, sorbitan ester ethoxylates such asTWEEN 80, TWEEN 20, PEG 600, PEG 400, PEG 300, or PEG-b-PPG-b-PEG may beadded to the formulation to generate porosity in the final films thatresults in lowering refractive index (RI) and increasing opticalperformance. The mechanism of the sol-gel will change and after initialcoating and solvent evaporation, the high boiling porogens may remainhomogenously dispersed in the thin film of gel. During thermal curing,the gel forms a stronger network of crosslink Si—O—Si bonding aroundhigh boiling porogens. The network structure is hard enough to keep itsshape at higher temperature when the burnable porogens evaporate andburn off. The void space produced from the loss of porogens results inpores which reduces the refractive index of the coating.

In another approach, a stable sol is made with the initial templateselected from the group consisting of ethylene oxide, propylene oxide,polyethylene oxides, polypropylene oxides, ethylene oxide/propyleneoxide block co-polymers, polyoxyethylted polyoxypropylated glycols,fatty acid ethoxylates, ethylene glycol esters, glycerol esters,mono-di-glycerides, glycerilesters, polyethylene glycolesters,polyglycerol esters, polyglyceryl esters, polyol monoesters,polypropylene glycol esters, polyoxyalkylene glycol esters,polyoxyalkylene propylene glycol esters, polyoxyalkylene polyol esters,polyoxyalkylene glyceride esters, polyoxyalkylene fatty acid, sorbitanesters, sorbitan fatty acid esters, sorbitan esters, polyoxyalkylenesorbitan esters, polyoxyethylen sorbitan monolurate, polyoxyethylenesorbitan monostearate, polyoxyethylene sorbitan tristearate, sorbitanester ethoxylates such as TWEEN 80, TWEEN 20, PEG 600, PEG 400, PEG 300,or PEG-b-PPG-b-PEG that is used as template followed by hydrolysis andcondensation of organoalkoxysilane and tetraalkoxysilane. Coating andcuring of the sol from this method produces high performanceanti-reflective coatings (ARC).

In yet another approach, a surfactant selected from a group of nonionicsurfactants, polyoxyethylene glycol alkyl ethers (Brij 58),polyoxyethylene octyl phenyl ether (TX-100), polyoxyethylene glycolsorbitan alkyl esters (polysorbate), ionic surfactants,cetyltrimethylammonium bromide and other tetraalkylammonium halides maybe added to the formulation in an amount of 0.0 to 5.0 wt % of the totalsol formulation.

To enhance silanol condensation, hence increasing cross-link density andlowering cure temperature, a Si—OH condensation catalyst selected fromthe group consisting of alkali metal hydroxide, amide, amines,imidazolines, such as; potassium hydroxide (KOH), sodium hydroxide(NaOH), cesium hydroxide (CsOH), ammonium hydroxide (NH4OH), tetramethylammonium hydroxide (TMAH), formamide (FA), dimethylformamide (DMF),N-methylpyrrolidinone (NMP), N,N-dimethyl acetamide (DMA), thermal basegenerator (TBG) or tetramethoxymethyl glycoluril (PowderLink 1174) maybe added to the formulations.

An optional adhesion promoter suitable for these compositions may beselected from organosilane compounds such as (meth)acryloxypropyltrimethoxysilane, (meth)acryloxypropyl triethoxysilane,(meth)acryloxypropyl dimethylmethoxysilane, (meth)acryloxypropylmethyldimethoxysilane, 3-glycidopropyl trimethoxysilane, 3-glycidopropyltriethoxysilane, 3-glycidopropyl dimethylmethoxysilane, 3-glycidopropylmethyldimethoxysilane and may be used in the amount of 0.1-5.0 weightpercent of the total sol formulation.

There are several methods by which the gel is dried and cured and/oraged to form the final coating. In some embodiments the gel is dried andcured under ambient or room temperature conditions. In some embodiments,the gel is aged under ambient conditions for 30 minutes followed bydrying for 3 hours in an oven kept at a variable relative humidity of(e.g., 20% to 50%). The temperature of the oven is then increased slowlyat a rate of 5° C./min to a final temperature of 120° C. The slowheating rate along with the moisture slows the rate of the silanolcondensation reaction to provide a more uniform and mechanically stablecoating. This method provides reproducible results and is a reliablemethod of making the coating with the desired properties.

In another embodiment, the gel on the substrate is heated under aninfrared lamp or array of lamps. These lamps are placed close proximityto the substrate's coated surface such that the surface is evenlyilluminated. The lamps are chosen for maximum emission in themid-infrared region of 3˜5 μm wavelength. This region is desirablebecause it is adsorbed better by glass than shorter infraredwavelengths. The power output of the lamps may be closely controlled viaa closed loop PID controller to achieve a precise and controllabletemperature profile. In some embodiments this profile will start fromambient temperature and quickly rise 1° C. to 50° C. per second to atemperature of 120° C., hold that temperature for a period of 30 to 300seconds, then reduce temperature back to ambient, with or without theaid of cooling airflow.

For applications requiring high throughput and/or for applicationswherein there is a process sensitivity around the maximum allowabletemperature for the bottom surface of the coated glass when the glass iscured it would be preferred to cure the glass such that only the topsurface of the glass is heated by impinging hot air on the coatedsurface or a xenon arc lamp using a pulsing method where the lamp isturned on and off multiple times during the cure cycle. One curingtechnique known as skin curing is described in greater detail elsewhereherein with reference to FIG. 17.

It is particularly noteworthy that some coatings of this disclosure maybe prepared under temperatures not exceeding 120° C. in contrast totemperatures of 400° C. to 600° C. typically employed in curingsilica-based anti-reflective coatings.

In another embodiment, the coating may be dried under ambient or roomtemperature conditions at variable relative humidity of (e.g., 20% to50%). Finally, the coating may be cured at a temperature selected from120° C. to 700° C. for periods of 5 min to 60 min.

In another embodiment, the coating may be dried under ambient or roomtemperature conditions at variable relative humidity of (e.g., 20% to50%). Then the coating is cured at tempering conditions.

As described above and as illustrated further in the examples, thecoatings made as described herein have several desirable properties. Thecoatings have anti-reflective properties that reduce the reflection ofphotons. The transmittance of a glass substrate coated with a coatingcomposition made according to the present disclosure can be increased byabout 1% to about 8%, from about 2% to about 6%, and from about 1% toabout 4% relative to uncoated glass substrates

The coatings also have anti-soiling properties, which are also importantin maintaining sufficient transmittance when used in conjunction with aglass substrate. Soiling is due to adherence of particulate matter onsurfaces exposed to environment. The deposition of the particles ontosurfaces depends upon the surface microstructure as well as chemicalcomposition. In general, rough surfaces can provide many sites forphysical binding of particulate matter.

The chemical composition of the surfaces is reflected in the surfaceenergy as measured by contact angles. Low energy surfaces (characterizedby high water contact angles) are usually less susceptible to binding ascompared to high energy surfaces with low water contact angles.Therefore, anti-soiling properties can be determined indirectly bymeasuring the coating's contact angle. The coatings herein providecontact angles ranging from about 10 degrees to about 178 degrees, fromabout 110 degrees to about 155 degrees, and from about 125 degrees toabout 175 degrees. The coatings of this disclosure minimize the photonflux losses due to soiling by about 50% relative to uncoated samples.

The coatings of the present disclosure also provide tunable mechanicalproperties. Nano-indentation is a method of used to measure themechanical properties of nanoscale materials especially thin films andcoatings. The testing instrument that is used for performing thenanoindentation tests is a Nanomechanical Test System (manufactured byHysitron, Inc., USA). This Nanomechanical Test System is ahigh-resolution nanomechanical test instrument that performs nano-scalequasi-static indentation by applying a force to an indenter tip whilemeasuring tip displacement into the specimen. During indentation, theapplied load and tip displacement are continuously controlled and/ormeasured, creating a load-displacement curve for each indent. From theload-displacement curve, nano-hardness and reduced elastic modulusvalues can be determined by applying the Oliver and Pharr method and apre-calibrated indenter tip area function and a pre-determined machinecompliance value. The instrument can also provide in-situ SPM (scanningprobe microscopy) images of the specimen before and after indentation.Such nanometer resolution imaging function is accomplished quickly andeasily by utilizing the same tip for imaging as for indentation. Thein-situ SPM imaging capability is not only useful in observing surfacefeatures, but also critical in positioning the indenter probe over suchfeatures for indentation tests.

Typically nanohardness and reduced elastic modulus will be determinedusing nano-indentation. The reduced elastic modulus has a relationshipwith the Young's modulus as shown in Equation 1. If Poisson's ratio forthe material to be tested is known then Young's modulus of it can becalculated. The Poisson's ratio for the diamond indenter is 0.07 and theYoung's modulus of the indenter is 1141 GPa.

$\begin{matrix}{\frac{1}{E_{r}} = {\frac{\left( {1 - v_{material}^{2}} \right)}{E_{material}} + \frac{\left( {1 - v_{indenter}^{2}} \right)}{E_{indenter}}}} & {{Eq}.\mspace{14mu} 1}\end{matrix}$

The nanoindentation tests were performed on 1 cm² samples cut fromcoated glass specimens made according to composition of Example 2 andExample 3. To obtain the hardness and modulus values for the coating,ten indents were performed on each sample. Loads of 15 μN were used forSample 5F and 25 μN for Sample 7J. All indents were performed throughin-situ SPM imaging. Table 1 summarizes the test conditions andparameters used in the nano-hardness and modulus tests.

TABLE 1 Nanohardness and Modulus Testing Conditions and ParametersSpecimens Sample 5F and Sample 7J Test instrument TriboIndenterIndentation Load 15, 25 μN Indenter Probe Tip Diamond Berkovich indentertip Temperature 74° F. Humidity 25% RH Environment Ambient air

Tables 2 and 3 present the nanohardness, H, and reduced elastic modulus,Er, measurement results. These tables also show values for the contactdepth, hc, of each indent. The test locations of these indents werechosen to ensure adequate spacing between measurements.

From Tables 2 and 3, it can be known that the average nanohardness washighest for Sample 7J (2.11 GPa) and lowest for Sample 5F (1.43 GPa).Average reduced elastic modulus was highest for Sample 7J (20.99 GPa)lowest for Sample 5F (13.51 GPa). These results further confirm that thehardness of the coatings of the disclosure can be tuned by changing theratios of organoalkoxysilane, tetraalkoxysilane andorganofluoroalkoxysilanes in the synthesis of sols from which thecoatings are obtained.

TABLE 2 Nanohardness and Reduced Elastic Modulus Test Results for Sample5F - Film Made from Composition of Example 2 Test Under H Er hc 15 μN(GPa) (GPa) (nm) 1 1.46 13.93 15.24 2 1.45 13.67 15.16 3 1.48 13.3814.98 4 1.46 13.21 15.13 5 1.48 13.37 15.02 6 1.34 13.50 16.04 7 1.4613.55 15.23 8 1.43 13.95 15.40 9 1.43 13.57 15.41 10  1.34 13.00 16.06Average 1.43 13.51 15.37 St. Dev 0.05 0.30 0.39

TABLE 3 Nanohardness and Reduced Elastic Modulus Test Results for Film7J - Film Made from Composition of Example 3 Test Under H Er hc 25 μN(GPa) (GPa) (nm) 1 2.09 20.76 15.87 2 2.04 20.75 16.10 3 2.09 20.5315.72 4 2.27 21.75 14.99 5 2.08 21.15 15.82 6 2.13 21.40 15.59 7 2.0920.78 15.80 8 2.03 21.20 16.09 9 2.15 21.22 15.59 10  2.11 20.30 15.78Average 2.11 20.99 15.73 St. Dev 0.07 0.44 0.31

Another series of nanoindentations tests using the conditions of table 4were carried out for the coating from example 19 cured under variousconditions.

TABLE 4 Nanohardness and Modulus Testing Conditions and Parameters.Specimens 6 types of ARC film Test instrument TriboIndenter IndenterProbe Tip Diamond Berkovich indenter tip Indentation Loads 60, 40, 20,17, and 15 μN Temperature 76° F. Humidity 37% RH Environment Ambient air

The cure conditions of coating from example 19 are summarized in Table5.

TABLE 5 Cure condition for coatings from example 19: Example 19 CureTemp/° C. Cure Time/min 19-1A 500 30 19-2A 250 10 19-3A 250 30 19-4A 27510 19-5A 275 30

The results of nanoindentation tests of the coating from example 19 aresummarized in Tables 6-10.

TABLE 6 Nanohardness and Reduced Elastic Modulus Test Results for 19-1AH E_(r) h_(c) Test (GPa) (GPa) (nm) 1 1.41 11.06 19.46 2 1.40 11.7019.57 3 1.39 11.18 19.71 4 1.38 11.31 19.78 5 1.37 11.11 19.91 Average1.39 11.27 19.69 S.D. 0.02 0.26 0.18

TABLE 7 Nanohardness and Reduced Elastic Modulus Test Results for 19-2AH E_(r) h_(c) Test (MPa) (GPa) (nm) 1 560.18 5.76 18.03 2 571.94 6.7617.68 3 515.26 6.26 19.23 4 528.28 6.39 18.84 5 541.52 6.75 18.44Average 543.44 6.38 18.44 S.D. 23.02 0.41 0.62

TABLE 8 Nanohardness and Reduced Elastic Modulus Test Results for 19-3AH E_(r) h_(c) Test (MPa) (GPa) (nm) 1 534.86 4.09 18.62 2 554.16 4.1618.10 3 531.54 4.15 18.70 4 533.17 4.14 18.68 5 542.68 4.16 18.43Average 539.28 4.14 18.51 S.D. 9.35 0.03 0.25

TABLE 9 Nanohardness and Reduced Elastic Modulus Test Results for 19-4AH E_(r) h_(c) Test (MPa) (GPa) (nm) 1 533.02 4.12 20.80 2 582.91 4.5019.35 3 572.94 4.53 19.68 4 581.83 4.51 19.44 5 567.28 4.41 19.65Average 567.60 4.41 19.78 S.D. 20.38 0.17 0.58

TABLE 10 Nanohardness and Reduced Elastic Modulus Test Results for 19-5AH E_(r) h_(c) Test (MPa) (GPa) (nm) 1 659.34 5.92 20.08 2 658.88 6.0820.12 3 676.19 5.63 19.67 4 677.19 5.63 19.67 5 672.63 5.52 19.72Average 668.85 5.76 19.85 S.D. 9.05 0.23 0.23

The coatings of the present disclosure also provide desirable abrasionresistance. Abrasion resistance can be defined as the ability of amaterial to withstand erosion due to frictional forces to preserve andmaintain its original shape and appearance. Abrasion resistance relatesto the strength of the intrinsic framework structure as well as tosurface features. Materials that do not have sufficient strength due tolack of long range bonding interactions tend to abrade easily.Similarly, materials with uneven surfaces or coatings with surfacein-homogeneities and asperities tend to wear due to frictional losses.Also, the leveling and smoothening of these asperities due to frictionleads to changes in optical transmission of the coating as the materialis abraded.

The coatings of the present disclosure pass the standard test formeasuring abrasion resistance of coatings on surfaces as definedaccording to European Standard EN1096.2 (Glass in Building, CoatedGlass). The test involves the action of rubbing a felt pad on the coatedglass. The felt rubbing pad is subjected to a to-and-fro translationmotion with a stroke length of 120±5 mm at a speed of 54-66 strokes/mincombined with a continuous rotation of the pad of 6 rpm or of a rotationof between 10° to 30° at the end of each stroke. The back and forthmotion along with the rotation constitutes 1 cycle. The specificationsof the circular felt rubbing pad include a diameter of 14-15 mm,thickness of 10 mm and density of 0.52 g/cm². The felt pad is attachedto a mechanical finger that is 15 mm to 20 mm is diameter and placedunder a load of 4 Newtons. The transmission between 380 nm and 1100 nmis measured to evaluate abrasion resistance and the standard dictates anabsolute change in transmission of no more that 0.5% with respect to areference sample.

TABLE 11 Varying of Abrasion Resistance by Changing The Ratio ofPrecursors on Tin-Sided TCO Glass Pre-Abrasion Post-Abrasion CompositionTransmission Gain Transmission Gain Example 2 2.56 1.69 Example 3 3.172.83 Example7 2.49 2.49 Example 8 2.08 1.83 Example 9 2.69 2.43 Example10 2.06 1.95

The coatings of the present disclosure have abrasion resistance that canbe tuned or modulated in a variety of ways. Examples in Table 11demonstrates how the abrasion resistance of the coatings from thisdisclosure can be tuned or modulated by changing sol composition fromwhich the coatings are obtained. It would be beneficial to be able toprovide coatings as in Example 3 that have a higher durability againstabrasion for solar modules or glass substrates that are exposed toabrasive natural environments like sandstorms or cleaning actions thatinvolve contacting the antireflective coatings with abrasives. In areaswhere the solar modules are unlikely to be exposed to significantabrasive environments it might be more beneficial to provide coatingsthat have a higher pre-abrasion transmission as in Example 2.

It is possible that the beneficial properties of the coating can also betuned by changing the molecular weight of the sols that comprise thecoating or changing the ratio of low and high molecular weightcomponents in the sols that comprise the coating or by the changing thepolydispersity of the sols that comprise the coating. Altering the pHand changing the catalysts used in the reaction could also be used tochange the molecular weights and molecular weight distribution orpolydispersity of the components in the sol. For example, changing thepolydispersity of the sols could impact how the polymerized silanemolecules pack together. This could have an impact on abrasionresistance of the cured coating. Another example is modifying thesurface characteristics of the final coating by the presence of lowmolecular weight hydrolyzed organofluoroalkoxysilane molecules in thesol. As the coating dries, these low molecular weight species could riseto the coatings surface and modify the wettability of the coating andthereby alter its anti-soiling and/or self-cleaning properties.

Gel Permeation Chromatography (GPC) is a technique that is used tocharacterize the molecular weight of polymers. We have used Waters GPCsystems for molecular weight analysis. The method details are as followsHPLC system: a 1515 isocratic pump equipped with 2707 Autosampler and 50uL loop, 2414 RI detector with column heater. Column and detector ovenheated to 40° C. Flow used was 1.0 ml/min. Four 4.6×300 mm GPC Styrenedivinylbenzene copolymer packed columns in-line for an effective MWrange were used. The columns came pre-equilibrated in THF and THF wasused as the eluent. Polystyrene narrow standards were used and thestandard curve was fit to a 3rd-order polynomial. Nine polystyrenestandards from approx. 530 MW to 50,000 were used. The Poly Styrenestandards were prepared at 10 mg/ml each in THF and diluted theirsamples 1:10 in THF for injections. Results are shown in FIG. 7 a andFIG. 7 b for sol made from Example 2. It can be seen that some of thesols used for preparation of coatings in this disclosure can have aweight average Molecular Weight (Mw) of less than 1000 and numberaverage molecular weight of (Mn) of less than 1000 with polydispersity(PD) of less than 1.2.

Yet another way to modulate the abrasion resistance of the coatings ofthe present disclosure is by changing the temperature at which thecoatings are cured after drying. Similar films when cured at ambienttemperature typically will have a lower abrasion resistance compared tofilms cured at 120° C. which can be lower than films cured at 200° C. or300° C. in a conventional oven.

In general, the various coatings of the present disclosure provide ameans of making a transparent substrate or glass transmit more photonswithout altering its intrinsic structure and other properties, alongwith passivating the surface so that it becomes resistant to theadhesion of water, dirt, soil, and other exogenous matter. Accordingly,the coating mixtures and resulting gels and coatings as described hereinhave numerous commercial applications.

Regarding the coating mixtures themselves, these may be packaged forcommercial sale as a coating mixture or commercial coating formulationfor others to use. For example, the coating mixtures may be provided asa liquid composition, for example, for subsequent small scale treatmentof glass in a treatment separate from their usage as windows in solar orarchitectural systems. In this case the coating mixture may be packagedfor sale as siloxane polymer mixture after the silane precursors havebeen hydrolyzed and partially condensed.

One or more of the following organic solvents may be used forformulation of sol in the coating mixture: methanol, ethanol,1-propanol, 2-propanol, 1-butanol, ethyl acetate, ethylene glycol,formamide, dimethylformamide, N-methylpyrrolidinone, propylene glycolmethy ether, 1-methoxy-2-propanol, propylene glycol, propylesne glycolmethyletheracetate, acetone, cyclohexanone, methylethylkeone,N,N-dimethyl acetamide, dimethylether, diethylether, 2-butanol,2-butanone, tetrahydrofuran, 1,2-diethoxyethane, diethyleneglycol, 1,2dimethoxyethane, dipropylene glycol monomethyl ether acetate, propyleneglycol, diamyl ether, diethyl oxalate, lactic acid butyl ester, dibutylether, 1-pentanol, dimethoxy ethane, 1-hexanol, 1-heptanol, ethyleneglycol, gamma-butyrolactone, triethylene glycol, methyl t-butyl ether.

In addition, the coating mixtures may be deposited and allowed to cureon a particular substrate that is subsequently packaged for sale as afinished assembly. In particular, the coating compositions of thepresent disclosure can be coated onto any transparent substrate that hashydrogen bond donor or hydrogen bond acceptor groups on the surface. Forexample, the coating can be applied as a treatment for a given glass orother transparent substrate before or after it has been integrated intoa device, such a solar cell, optical window or enclosure, for example,as part of a glass treatment process. In other embodiments, thedisclosure provides for the use of the coating compositions as anefficiency enhancement aid in architectural windows in building andhouses by the provision of anti-reflection benefits and/or by theprovision of anti-soiling benefits to augment the anti-reflectionbenefits. In other embodiments, the disclosure provides for the use ofthe coating compositions as an efficiency enhancement aid in treatmentof transparent surfaces that require regular cleaning to make themself-cleaning For example, the coatings can be used in conjunction withglass used in windows, windshields, screens, architecture, goggles,eyeglasses, etc.

In other embodiments, the disclosure provides for the use of the coatingcompositions as an efficiency enhancement aid in photovoltaic solarmodule assemblies (e.g., the outer cover of solar modules) by theprovision of anti-reflection benefits and/or by the provision ofanti-soiling benefits to augment the anti-reflection benefits. Thesedevices convert solar energy into electrical energy and rely uponefficient absorption of photons, and effects such as reflection,scattering, and loss of absorption due to adsorbed soil or dirtparticles can lead to reduced power output. As noted, the coatings ofthis disclosure when coated onto a glass surface reduces reflection ofphotons (the so-called anti-reflective property) and also reducesadsorption and binding of dirt, soil, and other particulate matter fromthe environment to boost the transmission of photons through the glassas well as to prevent reduction in photons associated with deposition ofparticulate matter onto the surface.

The coatings for solar module applications provide unique challengesthat are not present with coatings typically utilized in other commonapplications. The use of anti-reflective coating in solar modulesnecessitates long term exposure of solar radiation that usually resultsin extensive degradation of polymeric materials under prolonged UVexposure due to photolytic breakdown of bonds in these materials. Thecoating compositions of the present disclosure utilize silane precursorsthat when hydrolyzed, condensed and cured give rise to a network that issimilar to glass with Si—O—Si bonds that are stable to radiativebreakdown. An additional advantage of using silica based materials insolar applications is the intrinsic hardness of the material that makesthe coating resistant to scratches, indentations, and abrasion. Further,the coatings of the present disclosure provide for enhanced lighttransmittance across the entire solar region from about 350 nm to about1150 nm, which is desirable for solar applications.

Further, the siloxane polymer mixture resulting from the coatingcompositions of this disclosure do not need to be applied to the solarmodules during manufacturing and may be applied after manufacturing toavoid any interference with the solar module manufacturing process. Itis expected that the solar module maker themselves may be able to usethe composition of this disclosure to coat the modules at appropriatepoints within their manufacturing process. In such instances, theprovision of a stable siloxane polymer mixture, that can be usedaccording to the methods described herein, provides a direct means forthe applying the coating mixture after manufacture of the modules oreven after final installation of the modules. This may streamline themanufacturing process and enhance the economic value of existingmodules, either existing inventory or modules already installed and inuse, to which the coatings can be applied.

In one embodiment, the process of coating the solar modules consists ofpreparing the module surface, coating the surface with the finalsiloxane polymer mixture made in accordance with the present disclosure,drying the coating under ambient conditions, and curing the driedmodules at elevated temperature. The module surface is prepared bypolishing the module with a cerium oxide slurry, followed by washing themodule with water, and drying it under ambient temperature-pressureconditions for a period ranging from about 10 hours to about 12 hours.

Once the module surface is prepared, in one embodiment, the finalsiloxane polymer mixture of the present disclosure is deposited ontosolar modules by means of a flow coater. The siloxane polymer mixture isdeposited onto the modules via gravitational free flow of the liquidsiloxane polymer mixture from top to bottom. The solar modules areplaced on the mobile platform that moves at a rate that is optimal forthe free flow of the siloxane polymer mixture without introducing breakpoints in the liquid stream or introducing turbulent flow. The rate ofliquid flow and the rate of movement of platform carrying the solarmodule are optimized for deposition of uniform, crack-free coatings thatare homogenous, free of deformities, and characterized by uniformthickness.

More specifically, in one embodiment, the module is placed on a mobilestage that is connected to a computer and programmed to move at a speedranging, in some embodiments, from about 0.05 cm/s to about 300 cm/s, inother embodiments from about 0.1 cm/s to about 10 cm/s, and in otherembodiments from about 0.25 cm/s to about 0.5 cm/s. The siloxane polymermixture is then deposited onto the module surface using a computercontrolled nozzle dispensing unit such that the rate of flow of siloxanepolymer mixture is, in some embodiments, from about 5 ml/min to about 50ml/min, in other embodiments from about 5 ml/min to about 25 ml/min, andin other embodiments from about 10 ml/min to about 15 ml/min. The rateat which the siloxane polymer mixture is deposited is important forproper deposition of the coatings. Notably, the nozzle diameter of thesol can be adjusted to ensure appropriate flow rate, with diameters ofthe nozzle ranging from about 0.3 mm to about 0.9 mm.

A particularly advantageous aspect of using a siloxane polymer mixtureis that it is in a liquid state but is also viscous enough to spreadwithout breakdown of the stream. The uniformity of the coatings isfurther ensured by adjusting the flow rate and the rate of the movementof the platform containing the solar modules. For a given flow rate ofthe siloxane polymer mixture, if the rate of the movement of theplatform is too fast then it leads to rupture of the siloxane polymermixture stream causing uneven coatings. For a given flow rate of thesiloxane polymer mixture, if the rate of the movement of the platform istoo slow it results in excessive flow and material build up thatdeteriorates the uniformity of the films. Therefore, a specific optimumof siloxane polymer mixture flow rate and the platform movement areimportant to provide even, uniform, and homogenous coatings. The use ofspecific pH, solvent, and silane concentrations as outlined aboveprovide the ideal viscosities.

The coating process is also facilitated by the evaporation of thesolvent during the flow of the siloxane polymer mixture onto the panel,which also affects the development of uniform films or coatings on themodule surface. The coatings are formed when the free flowing siloxanepolymer mixture dries on the surface and forms a solid on the glasssurface. More specifically, the bottom edge of the sol represents theleading wet line while drying occurs at the top edge. As the solventevaporates, the siloxane polymer mixture becomes more viscous andfinally sets at the top edge while the bottom edge is characterized byliquid edge spreading. The spreading liquid at the bottom edge enablesthe free flow of the siloxane polymer mixture while the setting siloxanepolymer mixture at the top edge fixes the materials and preventsformation of lamellar structures. A balance of these factors isimportant for formation of uniform films.

The flow coating method does not allow seepage of the siloxane polymermixture into the internal parts of the solar module assembly as theexcess siloxane polymer mixture can be collected into a container at thebottom of the assembly and recycled. Similarly, it does not facilitatecorrosion and/or leaching of the chemicals from the interior of thesolar module assembly. The flow coater method exposes only the glassside to the siloxane polymer mixture while the other side of the moduleassembly, which may contain with electrical contacts and leads does notcome into any contact with the liquid siloxane polymer mixture. As such,the flow coating process is particular beneficial to coating solarmodules during either the assembly or the post-assembly stages.

The methods described here can be used to coat solar modules of variablesizes and in variable configurations. For example, typical modules havethe dimensions of about 1 m×1.6 m, which can be coated either inportrait configuration or landscape configurations mode via appropriateplacement in the mobile platform.

The flow coater can be used to coat the modules at the rate of about15-60 modules per hour. The rate of coating of individual modules woulddepend upon the size of the modules and whether they are coated in theportrait mode or landscape orientation. Additionally, multiple coatersoperating in parallel, or a single coater that runs along the entirelength can be used in conjunction with the module assembly line toincrease the production rate.

After depositing the coating, the module is dried for a period rangingfrom about 1 minute to about 20 minutes or longer under ambientconditions. The coated module is then cured using any of the techniquesfor curing described above, after which the coated module is ready foruse.

The anti-reflecting coatings described herein increase the peak power ofthe solar cells by approximately 3% due to the anti-reflective property.In addition, it is estimated that the anti-soiling property wouldcontribute to minimize transmissive losses associated with accumulationof dirt on the modules. Typical soiling losses are estimated at about 5%and use of these coatings is expected to reduce the losses in half.

EXAMPLES

The following describes various aspects of the coatings made accordingto certain embodiments of the disclosure in connection with the Figures.These examples should not be viewed as limiting. The general procedureused for the preparation of sol from a two-part process of acidcatalyzed hydrolysis of methyltrialkoxysilane and tetraalkoxysilane andfluoropropyltrialkoxysilane is described as follows:

Method I:

In the 1^(st) part of the two-part process of sol preparation, a 500 mlflask is charged with deionized water (DIW), hydrochloric acid (HCl),optional additive, and IPA stir @ 100 rpm at RT for short time (1 min)followed by addition of methyltrialkoxysilane. The reaction is stirredat ˜100 rpm at RT for 30 min. Similarly 2 ^(nd) part of the sol wasprepared by charging a 500 ml flask with DIW, HCl and IPA stir @ 100 rpmfor short time (˜1 min) followed by addition oftrifluoropropyltrialkoxysilane. The 2^(nd) part is stirred at ˜100 rpmat RT for 30 min. The 1^(st) and 2^(nd) parts of the sol are combinedand tetraalkoxysilane is added to this mixture and stirred for another30 minutes at ˜100 rpm at RT. The final sol product mixture is aged for48 hours at RT and then characterized by GPC and NMR.

Method II:

In the one part 2-step process of preparation of the sol, a 500 ml flaskis charged with DIW, HCl, optional additive, and IPA stir @ 100 rpm atRT for short time (1 min) followed by addition of methyltrialkoxysilane.The reaction is stirred at ˜100 rpm at RT for 30 min. Tetraalkoxysilaneis added to this mixture and stirred for another 30 minutes at ˜100 rpmat RT. The final sol product mixture is aged for 48 hours at RT and thencharacterized by GPC and NMR.

Method III:

In the one part 2-step process of preparation of the sol, a 500 ml flaskis charged with DIW, HCl, optional additive, and IPA stir @ 100 rpm atRT for short time (1 min) followed by addition of tetraalkoxysilane. Thereaction is stirred at ˜100 rpm at RT for 30 min. Methyltrialkoxysilaneis added to this mixture and stirred for another 30 minutes at ˜100 rpmat RT. The final sol product mixture is aged for 48 hours at RT and thencharacterized by GPC and NMR.

Method IV:

In the one part 2-step process of preparation of the sol, a 500 ml flaskis charged with DIW, HCl, optional additive, and IPA stir @ 100 rpm atRT for short time (1 min) followed by addition of tetraalkoxysilane. Thereaction is stirred at ˜100 rpm at RT for 30 min. A mixture oftrifluoropropyltrialkoxysilane and methyltrialkoxysilane is added tothis mixture and stirred for another 30 minutes at ˜100 rpm at RT. Thefinal sol product mixture is aged for 48 hours at RT and thencharacterized by GPC and NMR.

In one embodiment referred to as Example 1, following method I, Sol I isprepared by charging a 500 mL flask with 177 g of IPA and 25 g of 0.04 MHCl. After stirring @ 100 rpm at RT for short time (˜1 min), 2.87 g(0.021 moles) of methyltrimethoxysilane (MTMOS) is added to the mixture.The mixture is stirred at RT for 30 min. Sol II is prepared by charginga 500 mL flask with 177 g of IPA and 25 g of 0.04 M HCl. After stirring@ 100 rpm at RT for short time (˜1 min), 3.71 g (0.021 moles) of(3,3,3-trifluoropropyl)-trimethoxysilane (F3TMOS) is added to themixture. The mixture is stirred at RT for 30 min. Sol I and II are mixedtogether followed by addition of 6.39 g (0.042 moles) oftetramethoxysilane (TMOS). The final mixture is stirred at RT for 30min. This mixture is allowed to age under ambient conditions for 24hours up to 120 hours. After aging the sol formulation, 30×30 cm glasssheets (polished with cerium oxide polish, washed, and allowed to dry)are flow coated with the final sol mixture and allowed to dry forapproximately 1-10 minutes followed by curing at temperature of 120° C.for 60 minutes.

In another embodiment referred to as Example 2, following method I, SolI is prepared by charging a 500 mL flask with 177 g of IPA and 25 g of0.04 M HCl. After stirring @ 100 rpm at RT for short time (˜1 min), 2.87g (0.021 moles) of methyltrimethoxysilane (MTMOS) is added to themixture. The mixture is stirred at RT for 30 min. Sol II is prepared bycharging a 500 mL flask with 177 g of IPA and 25 g of 0.04 M HCl. Afterstirring @ 100 rpm at RT for short time (˜1 min), 3.71 g (0.021 moles)of (3,3,3-trifluoropropyl)-trimethoxysilane (F3TMOS) is added to themixture. The mixture is stirred at RT for 30 min. Sol I and II are mixedtogether followed by addition of 8.8 g (0.042 moles) oftetraethoxysilane (TEOS). The final mixture is stirred at RT for 30 min.This mixture is allowed to age under ambient conditions for 48 hours.The GPC test of the final sol produced molecular weight of Mw=1,137g/mol with polydispersity PD=1.13. After aging the sol formulation,30×30 cm glass sheets (polished with cerium oxide polish, washed, andallowed to dry) are flow coated with the final sol mixture and allowedto dry for approximately 1-10 minutes followed by curing at temperatureof 120° C. for 60 minutes. Typical GPC results are shown in FIGS. 7 a-1and 7 a-2 and the Si—NMR results are shown in FIG. 21 and FIG. 22. AnSEM cross-section of a representative sample of cured film from example2 is shown in FIG. 4.

A TEM cross-section of a representative sample of the dried and curedfilm from example 2 is shown in FIG. 3 a. TEM cross-section and the HighResolution TEM of the film from example 2 show no evidence of long rangeorder within the film. The film morphology at a scale 5 nm shows littleevidence of porosity.

In yet another embodiment referred to as Example 3, following method IIthe sol is prepared by charging a 500 mL flask with 354 g of IPA and 50g of 0.04 M HCl. After stirring @ 100 rpm at RT for short time (˜1 min),4.37 g (0.0321 moles) of methyltrimethoxysilane (MTMOS) is added to themixture. The mixture is stirred at RT for 30 min followed by addition of7.08 g (0.034 moles) of tetraethoxysilane (TEOS). The final mixture isstirred at RT for 30 min. This mixture is allowed to age under ambientconditions for 48 hours. The GPC test of the final sol producedmolecular weight of Mw=906 g/mol with polydispersity PD=1.10. 30×30 cmglass sheets (polished with cerium oxide polish, washed, and allowed todry) are flow coated with the final sol mixture and allowed to dry forapproximately 1-10 minutes followed by curing at temperature of 120° C.for 60 minutes. GPC results are shown in FIGS. 7 b-1 and 7 b-2, and NMRresults are shown in FIG. 21 and FIG. 22. SEM cross-section of arepresentative sample of cured film from example 3 is shown in FIG. 5.

In yet another embodiment referred to as Example 4, following method I,Sol I is prepared by charging a 500 mL flask with 177 g of IPA and 25 gof 0.04 M HCl. After stirring @ 100 rpm at RT for short time (˜1 min),2.63 g (0.0193 moles) of methyltrimethoxysilane (MTMOS) is added to themixture. The mixture is stirred at RT for 30 min. Sol II is prepared bycharging a 500 mL flask with 177 g of IPA and 25 g of 0.04 M HCl. Afterstirring @ 100 rpm at RT for short time (˜1 min), 0.284 g (0.0013 moles)of (3,3,3-trifluoropropyl)-trimethoxysilane (F3TMOS) is added to themixture. The mixture is stirred at RT for 30 min. Sol I and II are mixedtogether followed by addition of 6.24 g (0.03 moles) oftetraethoxysilane (TEOS). The final mixture is stirred at RT for 30 min.This mixture is allowed to age under ambient conditions for 48 hours.The GPC test of the final sol produced molecular weight of Mw=690 g/molwith polydispersity PD=1.10. 30×30 cm glass sheets (polished with ceriumoxide polish, washed, and allowed to dry) are flow coated with the finalsol mixture and allowed to dry for approximately 1-10 minutes followedby curing at temperature of 120° C. for 60 minutes. GPC results areshown in FIGS. 7 c-1 and 7 c-2. SEM cross-section of a representativesample of cured film from example 4 is shown in FIG. 6.

In yet another embodiment referred to as Example 5, following method I,Sol I is prepared by charging a 500 mL flask with 177 g of IPA and 25 gof 0.04 M HCl. After stirring @ 100 rpm at RT for short time (˜1 min),2.39 g (0.01753 moles) of methyltrimethoxysilane (MTMOS) is added to themixture. The mixture is stirred at RT for 30 min. Sol II is prepared bycharging a 500 mL flask with 177 g of IPA and 25 g of 0.04 M HCl. Afterstirring @ 100 rpm at RT for short time (˜1 min), 0.399 g (0.00262moles) of (3,3,3-trifluoropropyl)-trimethoxysilane (F3TMOS) is added tothe mixture. The mixture is stirred at RT for 30 min. Sol I and II aremixed together followed by addition of 6.24 g (0.03 moles) oftetraethoxysilane (TEOS). The final mixture is stirred at RT for 30 min.This mixture is allowed to age under ambient conditions for 48 hours.The GPC test of the final sol produced molecular weight of Mw=1,190g/mol with polydispersity PD=1.25. 30×30 cm glass sheets (polished withcerium oxide polish, washed, and allowed to dry) are flow coated withthe final sol mixture and allowed to dry for approximately 1-10 minutesfollowed by curing at temperature of 120° C. for 60 minutes. GPC resultsare shown in FIGS. 7 d-1 and 7 d-2.

In yet another embodiment referred to as Example 6, following method I,sol I is prepared by charging a 500 mL flask with 177 g of IPA and 25 gof 0.04 M AcOH (acetic acid). After stirring @ 100 rpm at RT for shorttime (˜1 min), 2.32 g (0.017 moles) of methyltrimethoxysilane (MTMOS) isadded to the mixture. The mixture is stirred at RT for 30 min. Sol II isprepared by charging a 500 mL flask with 177 g of IPA and 25 g of 0.08 MAcOH. After stirring @ 100 rpm at RT for short time (˜1 min), 3.71 g(0.017 moles) of (3,3,3-trifluoropropyl)-trimethoxysilane (F3TMOS) isadded to the mixture. The mixture is stirred at RT for 30 min. Sol I andII are mixed together followed by addition of 7.08 g (0.034 moles) oftetraethoxysilane (TEOS). The final mixture is stirred at RT for 30 min.This mixture is allowed to age under ambient conditions for 48 hours.The GPC test of the final sol produced molecular weight of Mw=2,370g/mol with polydispersity PD=1.85. 30×30 cm glass sheets (polished withcerium oxide polish, washed, and allowed to dry) are flow coated withthe final sol mixture and allowed to dry for approximately 1-10 minutesfollowed by curing at temperature of 120° C. for 60 minutes. GPC resultsare shown in FIGS. 7 e-1 and 7 e-2.

In yet another embodiment referred to as Example 7, following method IIthe sol is prepared by charging a 500 mL flask with 354 g of IPA and 50g of 0.08 M AcOH. After stirring @ 100 rpm at RT for short time (˜1min), 9.13 g (0.067 moles) of methyltrimethoxysilane (MTMOS) is added tothe mixture. The mixture is stirred at RT for 30 min followed byaddition of 13.96 g (0.067 moles) of tetraethoxysilane (TEOS). The finalmixture is stirred at RT for 30 min. This mixture is allowed to ageunder ambient conditions for 48 hours. The GPC test of the final solproduced molecular weight of Mw=926 g/mol with polydispersity PD=1.32.30×30 cm glass sheets (polished with cerium oxide polish, washed, andallowed to dry) are flow coated with the final sol mixture and allowedto dry for approximately 1-10 minutes followed by curing at temperatureof 120° C. for 60 minutes. GPC results are shown in FIGS. 7 f-1 and 7f-2.

In yet another embodiment referred to as Example 8, following method IIthe sol is prepared by charging a 500 mL flask with 354 g of IPA and 50g of 0.08 M HCl. After stirring @ 100 rpm at RT for short time (˜1 min),9.13 g (0.067 moles) of methyltrimethoxysilane (MTMOS) is added to themixture. The mixture is stirred at RT for 30 min followed by addition of13.96 g (0.067 moles) of tetraethoxysilane (TEOS). The final mixture isstirred at RT for 30 min. This mixture is allowed to age under ambientconditions for 48 hours. The GPC test of the final sol producedmolecular weight of Mw=805 g/mol with polydispersity PD=1.12. 30×30 cmglass sheets (polished with cerium oxide polish, washed, and allowed todry) are flow coated with the final sol mixture and allowed to dry forapproximately 1-10 minutes followed by curing at temperature of 120° C.for 60 minutes. GPC results are shown in FIGS. 7 g-1 and 7 g-2.

In yet another embodiment referred to as Example 9, following method IIthe sol is prepared by charging a 500 mL flask with 354 g of IPA and 50g of 0.08 M HCl. After stirring @ 100 rpm at RT for short time (˜1 min),9.13 g (0.067 moles) of methyltrimethoxysilane (MTMOS) is added to themixture. The mixture is stirred at RT for 30 min followed by addition of13.96 g (0.067 moles) of tetraethoxysilane (TEOS). The final mixture isstirred at RT for 30 min. This mixture is allowed to age under ambientconditions for 48 hours. The GPC test of the final sol producedmolecular weight of Mw=857 g/mol with polydispersity PD=1.12. 30×30 cmglass sheets (polished with cerium oxide polish, washed, and allowed todry) are flow coated with the final sol mixture and allowed to dry forapproximately 1-10 minutes followed by curing at temperature of 120 ° C.for 60 minutes. GPC results are shown in FIGS. 7 h-1 and 7 h-2.

In yet another embodiment referred to as Example 10, following method IIthe sol is prepared by charging a 500 mL flask with 197 g of IPA and 140g of 0.08 M HCl. After stirring @ 100 rpm at RT for short time (˜1 min),30.2 g (0.288) of methyltrimethoxysilane (MTMOS) is added to themixture. The mixture is stirred at RT for 30 min followed by addition of60 g (0.288 moles) of tetraethoxysilane (TEOS). The final mixture isstirred at RT for 30 min. This mixture is allowed to age under ambientconditions for 48 hours. The GPC test of the final sol producedmolecular weight of Mw=1,635 g/mol with polydispersity PD=1.40. 30×30 cmglass sheets (polished with cerium oxide polish, washed, and allowed todry) are flow coated with the final sol mixture and allowed to dry forapproximately 1-10 minutes followed by curing at temperature of 120° C.for 60 minutes. GPC results are shown in FIGS. 7 k-1 and 7 k-2.

In yet another embodiment referred to as Example 11, sol from example 8is formulated with 6.4 g of Tween 80. 30×30 cm glass sheets (polishedwith cerium oxide polish, washed, and allowed to dry) are flow coatedwith the final sol mixture and allowed to dry for approximately 1-10minutes followed by thermal curing.

In yet another embodiment referred to as Example 12, sol from example 8is formulated with 4.27 g of Tween 80. 30×30 cm glass sheets (polishedwith cerium oxide polish, washed, and allowed to dry) are flow coatedwith the final sol mixture and allowed to dry for approximately 1-10minutes followed by thermal curing.

In yet another embodiment referred to as Example 13, sol from example 8is formulated with 2.14 g of Tween 80. 30×30 cm glass sheets (polishedwith cerium oxide polish, washed, and allowed to dry) are flow coatedwith the final sol mixture and allowed to dry for approximately 1-10minutes followed by thermal curing.

In yet another embodiment referred to as Example 14, following method IIthe sol is prepared by charging a 500 mL flask with 354 g of IPA, 0.66 g(0.011 moles)of B(OH)₃ and 50 g of 0.08 M HCl. After stirring @ 100 rpmat RT for short time (˜1 min), 9.13 g (0.067 moles) ofmethyltrimethoxysilane (MTMOS) is added to the mixture. The mixture isstirred at RT for 30 min followed by addition of 13.96 g (0.067 moles)of tetraethoxysilane (TEOS). The final mixture is stirred at RT for 30min. This mixture is allowed to age under ambient conditions for 48hours. The GPC test of the final sol produced molecular weight ofMw=826/mol with polydispersity PD=1.07. 30×30 cm glass sheets (polishedwith cerium oxide polish, washed, and allowed to dry) are flow coatedwith the final sol mixture and allowed to dry for approximately 1-10minutes followed by thermal curing.

In yet another embodiment referred to as Example 15, sol from example 8is formulated with 6.4 g of Tween 80 and 6.4 g of AlCl₃. 30×30 cm glasssheets (polished with cerium oxide polish, washed, and allowed to dry)are flow coated with the final sol mixture and allowed to dry forapproximately 1-10 minutes followed by thermal curing.

In yet another embodiment referred to as Example 16, sol from example 8is formulated with 6.4 g of Tween 20. 30×30 cm glass sheets (polishedwith cerium oxide polish, washed, and allowed to dry) are flow coatedwith the final sol mixture and allowed to dry for approximately 1-10minutes followed by thermal curing.

In yet another embodiment referred to as Example 17, sol from example 8is formulated with 4.27 g of Tween 20. 30×30 cm glass sheets (polishedwith cerium oxide polish, washed, and allowed to dry) are flow coatedwith the final sol mixture and allowed to dry for approximately 1-10minutes followed by thermal curing.

In yet another embodiment referred to as Example 18, sol from example 8is formulated with 2.14 g of Tween 20. 30×30 cm glass sheets (polishedwith cerium oxide polish, washed, and allowed to dry) are flow coatedwith the final sol mixture and allowed to dry for approximately 1-10minutes followed by thermal curing.

In yet another embodiment referred to as Example 19, sol from example 8is formulated with 6.4 g of PEG 600. 30×30 cm glass sheets (polishedwith cerium oxide polish, washed, and allowed to dry) are flow coatedwith the final sol mixture and allowed to dry for approximately 1-10minutes followed by thermal curing.

In yet another embodiment referred to as Example 20, sol from example 8is formulated with 6.4 g of PEG 400. 30×30 cm glass sheets (polishedwith cerium oxide polish, washed, and allowed to dry) are flow coatedwith the final sol mixture and allowed to dry for approximately 1-10minutes followed by thermal curing.

In yet another embodiment referred to as Example 21, sol from example 8is formulated with 6.4 g of PEG 300. 30×30 cm glass sheets (polishedwith cerium oxide polish, washed, and allowed to dry) are flow coatedwith the final sol mixture and allowed to dry for approximately 1-10minutes followed by thermal curing.

In yet another embodiment referred to as Example 22, following method IIthe sol is prepared by charging a 500 mL flask with 354 g of IPA, 6.4 gof Tween 80 and 50 g of 0.08 M HCl. After stirring @ 100 rpm at RT forshort time (˜1 min), 9.13 g (0.067 moles) of methyltrimethoxysilane(MTMOS) is added to the mixture. The mixture is stirred at RT for 30 minfollowed by addition of 13.96 g (0.067 moles) of tetraethoxysilane(TEOS). The final mixture is stirred at RT for 30 min. This mixture isallowed to age under ambient conditions for 48 hours. The GPC test ofthe final sol produced molecular weight of Mw=1558 g/mol withpolydispersity PD=1.34. 30×30 cm glass sheets (polished with ceriumoxide polish, washed, and allowed to dry) are flow coated with the finalsol mixture and allowed to dry for approximately 1-10 minutes followedby thermal curing.

In yet another embodiment referred to as Example 23, following method IIthe sol is prepared by charging a 500 mL flask with 354 g of IPA, 6.4 gof PEG 600 and 50 g of 0.08 M HCl. After stirring @ 100 rpm at RT forshort time (˜1 min), 9.13 g (0.067 moles) of methyltrimethoxysilane(MTMOS) is added to the mixture. The mixture is stirred at RT for 30 minfollowed by addition of 13.96 g (0.067 moles) of tetraethoxysilane(TEOS). The final mixture is stirred at RT for 30 min. This mixture isallowed to age under ambient conditions for 48 hours. The GPC test ofthe final sol produced molecular weight of Mw=988 g/mol withpolydispersity PD=1.1. 30×30 cm glass sheets (polished with cerium oxidepolish, washed, and allowed to dry) are flow coated with the final solmixture and allowed to dry for approximately 1-10 minutes followed bythermal curing.

In yet another embodiment referred to as Example 24, following method IIthe sol is prepared by charging a 500 mL flask with 354 g of IPA, 6.4 gof PEG-b-PPG-b-PEG and 50 g of 0.08 M HCl. After stirring @ 100 rpm atRT for short time (˜1 min), 9.13 g (0.067 moles) ofmethyltrimethoxysilane (MTMOS) is added to the mixture. The mixture isstirred at RT for 30 min followed by addition of 13.96 g (0.067 moles)of tetraethoxysilane (TEOS). The final mixture is stirred at RT for 30min. This mixture is allowed to age under ambient conditions for 48hours. The GPC test of the final sol produced molecular weight ofMw=1333 g/mol with polydispersity PD=1.17. 30×30 cm glass sheets(polished with cerium oxide polish, washed, and allowed to dry) are flowcoated with the final sol mixture and allowed to dry for approximately1-10 minutes followed by thermal curing.

In yet another embodiment referred to as Example 25, a 500 mLthree-necked flask fitted with two addition funnels and thermocoupletemperature sensor is cooled in an ice bath. One of the addition funnelsis charged with a mixture 32 g (0.235 moles) of methyltrimethoxysilane(MTMOS) 29 g of IPA, and 1.6 g of glacial AcOH. The other funnel ischarged with 100 g of a 34 weight % colloidal silica (Nalco 1034A). Thecolloidal silica and MTMOS solutions are added drop wise at such a ratethat the temperature of the reaction mixture does not exceed 5° C. Afterthe addition is complete, the mixture is allowed to warm to ambienttemperature with continued stirring and allowed to stand overnight. Themixture (151 g) diluted with IPA (757 g). This mixture is allowed to ageunder ambient conditions for 48 hours. The GPC test of the final solproduced molecular weight of Mw=685 g/mol with polydispersity PD=1.1.30×30 cm glass sheets (polished with cerium oxide polish, washed, andallowed to dry) are flow coated with the final sol mixture and allowedto dry for approximately 1-10 minutes followed by thermal curing.

In yet another embodiment referred to as Example 26, a 500 mLthree-necked flask fitted with two addition funnels and thermocoupletemperature sensor is cooled in an ice bath. One of the addition funnelsis charged with a mixture 17 g (0.125 moles) of methyltrimethoxysilane(MTMOS) 29 g of IPA, and 1.68 g of glacial AcOH. The other funnel ischarged with 100 g of a 34 weight % colloidal silica (Nalco 1034A). Thecolloidal silica and MTMOS solutions are added drop wise at such a ratethat the temperature of the reaction mixture does not exceed 5° C. Afterthe addition is complete, the mixture is allowed to warm to ambienttemperature with continued stirring and allowed to stand overnight. Themixture (140 g) diluted with IPA (853.5 g). This mixture is allowed toage under ambient conditions for 48 hours. The GPC test of the final solproduced molecular weight of Mw=637 g/mol with polydispersity PD=1.07.30×30 cm glass sheets (polished with cerium oxide polish, washed, andallowed to dry) are flow coated with the final sol mixture and allowedto dry for approximately 1-10 minutes followed by thermal curing.

In yet another embodiment referred to as Example 27, a 500 mLthree-necked flask fitted with two addition funnels and thermocoupletemperature sensor is cooled in an ice bath. One of the addition funnelsis charged with a mixture 8 g (0.059 moles) of methyltrimethoxysilane(MTMOS) 28 g of IPA, and 1.68 g of glacial AcOH. The other funnel ischarged with 100 g of a 34 weight % colloidal silica (Nalco 1034A). Thecolloidal silica and MTMOS solutions are added drop wise at such a ratethat the temperature of the reaction mixture does not exceed 5° C. Afterthe addition is complete, the mixture is allowed to warm to ambienttemperature with continued stirring and allowed to stand overnight. Themixture (151 g) diluted with IPA (757 g). This mixture is allowed to ageunder ambient conditions for 48 hours. The GPC test of the final solproduced molecular weight of Mw=567 g/mol with polydispersity PD=1.03.30×30 cm glass sheets (polished with cerium oxide polish, washed, andallowed to dry) are flow coated with the final sol mixture and allowedto dry for approximately 1-10 minutes followed by thermal curing.

In yet another embodiment referred to as Example 28. The final sol fromexample 27 is formulated with 1.79 g of 10 weight % solution ofPowderLink in NMP. 30×30 cm glass sheets (polished with cerium oxidepolish, washed, and allowed to dry) are flow coated with the final solmixture and allowed to dry for approximately 1-10 minutes followed bythermal curing.

In yet another embodiment referred to as Example 29. The final sol fromexample 23 is formulated with 1.79 g of 10 weight % solution ofPowderLink in NMP. 30×30 cm glass sheets (polished with cerium oxidepolish, washed, and allowed to dry) are flow coated with the final solmixture and allowed to dry for approximately 1-10 minutes followed bythermal curing.

In yet another embodiment referred to as Example 30. The final sol fromexample 23 is formulated with 3.58 g of 10 weight % solution ofPowderLink in NMP. 30×30 cm glass sheets (polished with cerium oxidepolish, washed, and allowed to dry) are flow coated with the final solmixture and allowed to dry for approximately 1-10 minutes followed bythermal curing.

In yet another embodiment referred to as Example 31. The final sol fromexample 11 is formulated with 2.17 g (0.0067 moles) of Al(acac)₃. 30×30cm glass sheets (polished with cerium oxide polish, washed, and allowedto dry) are flow coated with the final sol mixture and allowed to dryfor approximately 1-10 minutes followed by thermal curing.

In yet another embodiment referred to as Example 32, following method IIthe sol is prepared by charging a 500 mL flask with 354 g of IPA, 8.09 gof Al Cl₃. 6H₂O and 6.4 g of Tween-80 and 50 g of 0.08 M HCl. Afterstirring @ 100 rpm at RT for short time (˜1 min), 9.13 g (0.067 moles)of methyltrimethoxysilane (MTMOS) is added to the mixture. The mixtureis stirred at RT for 30 min followed by addition of 13.96 g (0.067moles) of tetraethoxysilane (TEOS). The final mixture is stirred at RTfor 30 min. This mixture is allowed to age under ambient conditions for48 hours. The GPC test of the final sol produced molecular weight ofMw=1732 g/mol with polydispersity PD=1.41. 30×30 cm glass sheets(polished with cerium oxide polish, washed, and allowed to dry) are flowcoated with the final sol mixture and allowed to dry for approximately1-10 minutes followed by thermal curing.

In yet another embodiment referred to as Example 33, following methodIII the sol is prepared by charging a 500 ml flask with 345 g of IPA,and 50 g of 0.08 M HCl. After stirring @ 100 rpm at RT for short time(˜1 min), 13.96 g (0.067 moles) of tetraethoxysilane (TEOS) is added tothe mixture. The mixture is stirred at RT for 30 min followed byaddition of 9.13 g (0.067 moles) of methyltrimethoxysilane (MTMOS). Thefinal mixture is stirred at RT for 30 min. This mixture is allowed toage under ambient conditions for 48 hours. The GPC test of the final solproduced molecular weight of Mw=886 g/mol with polydispersity PD=1.07.30×30 cm glass sheets (polished with cerium oxide polish, washed, andallowed to dry) are flow coated with the final sol mixture and allowedto dry for approximately 1-10 minutes followed by thermal curing.

In yet another embodiment referred to as Example 34, sol from example 33is formulated with 6.4 g of PEG 600. 30×30 cm glass sheets (polishedwith cerium oxide polish, washed, and allowed to dry) are flow coatedwith the final sol mixture and allowed to dry for approximately 1-10minutes followed by thermal curing.

In yet another embodiment referred to as Example 35, following methodIII the sol is prepared by charging a 500 ml flask with 345 g of IPA,and 50 g of 0.08 M HCl. After stirring @ 100 rpm at RT for short time(˜1 min), 12.6 g (0.061 moles) of tetraethoxysilane (TEOS) is added tothe mixture. The mixture is stirred at RT for 30 min followed byaddition of 5.73 g (0.042 moles) of methyltrimethoxysilane (MTMOS) and6.85 g (0.033 moles) of (3,3,3-trifluoropropyl)-trimethoxysilane(F3TMOS) and the final mixture is stirred at RT for 30 min. This mixtureis allowed to age under ambient conditions for 48 hours. The GPC test ofthe final sol produced molecular weight of Mw=717 g/mol withpolydispersity PD=1.01. 30×30 cm glass sheets (polished with ceriumoxide polish, washed, and allowed to dry) are flow coated with the finalsol mixture and allowed to dry for approximately 1-10 minutes followedby thermal curing.

Where applicable, the measurement of anti-reflective properties of thecoatings is done as follows: The transmittance of the coatings ismeasured by means of UV-vis absorption spectrophotometer equipped withan integrator accessory. The anti-reflective enhancement factor ismeasured as the relative percent increase in transmittance compared tountreated glass slides versus glass slides coated with compositions ofthis disclosure. ASTM E424 describes the solar transmission gain, whichis defined as the relative percent difference in transmission of solarradiation before and after the application of the coating. The coatingsexhibit about 1.5% to about 3.25% gain in solar transmission. Therefractive index of the coating is measured by an ellipsometer.

The abrasion resistance of the coating is measured by an abrader deviceaccording to European standard EN1096.2 (glass in building coatedglass). The coatings made according to Examples 1, 2, 3, 4, 5, 6, 7, 8,9,and 10 without any added composition modifying additives, are ablemeet the passing criteria of the standard. Coatings made from Example 3,7, 8, 9, 10 are exceptional in that it is able to have almost no damageafter 500 cycles of testing per the EN1096 standard. Abrasion losses areless than 0.5%.

The contact angle of the coatings is measured by means of goniometerwherein the contact angle of the water droplet is measured by means of aCCD camera. An average of three measurements is used for each sample. Ontin-sided float glass, average contact angles for coatings made fromExamples 2, 4, 5 and 6 measure 85° and on tin-sided TCO glass, averagecontact angles measure 90°.

The reliability results of the coatings in this disclosure are broadlysimilar to existing anti-reflective coatings. However, under 85° C./85%RH test conditions per IEC61215 and IEC61646 the coatings of thisdisclosure have a protective effect on glass corrosion which is notobserved when highly porous anti-reflective sol-gel coatings are testedunder similar conditions. Without being bound to theory, we believe thatporous anti-reflective coatings facilitate easy leaching of sodium ionsfrom the glass whereas the coatings of this disclosure can be tuned toachieve hydrophobic properties which slow down the rate and/or decreasethe amount of water that is contact with the glass. Coatings made fromexamples 2, 4, 5 and 6 of this disclosure exhibit minimal glasscorrosion compared to uncoated glass. The other remarkable feature ofthe passing reliability results is that these reliability results havebeen achieved with a coating cured at just 120° C. Existinganti-reflective coatings are typically sintered at 400˜700° C. toachieve the level of reliability indicated by these results.

FIG. 1 a illustrates the UV-vis transmittance spectra showing maximumtransmittance enhancement of coatings on tin side of float glass fromcomposition given in Example 2. A statistical comparison of 11 samplesfrom coating made from composition in Example 2 on tin side vs non-tinside of float glass provided a solar weighted photon gain of 2.23% vs1.93%. Without being bound to theory, the coatings of this disclosureinteract with the tin side of float glass to provide an enhancement inthe beneficial properties of the antireflective coatings.

FIG. 1 b illustrates the UV-vis transmittance spectra of roll coatedcoating made from Example 3 on patterned glass substrate

FIG. 2 a illustrates the UV-vis transmittance spectra showing maximumtransmittance enhancement of coatings on tin side of TCO glasssubstrates made from compositions given in Example 3 comparing pre- andpost-abrasion spectra.

FIGS. 2 b and 2 c illustrates the UV-vis transmittance spectra ofcoatings made from example 5 and Sols from the three formulations couldhave different inherent viscosities and it would be preferable to beable to tune the viscosities of the sols such that their solar weightedphoton gain is maximized.

FIG. 3 a is a TEM cross-sectional view of a coating made from thecomposition of Example 2 on a glass slide substrate. The TEM images showthe absence of any discernible porosity in these coatings. The filmthickness about 70-80 nm.

FIG. 3 b is a HRTEM of a coating made from the composition of Example 2on a glass slide.

FIG. 4 is an SEM cross-sectional view of a coating made from thecomposition of Example 2 on a 30×30 cm float glass substrate. The SEMimages show the absence of porosity and a film thickness of 133 nm.

FIG. 5 is an SEM cross-sectional view of a coating made from thecomposition of Example 3 on a 30×30 cm float glass substrate. The SEMimages show the absence of porosity and a film thickness of ˜83 nm.

FIG. 6 is an SEM cross-sectional view of a coating made from thecomposition of Example 4 on a 30×30 cm float glass substrate. The SEMimages show the absence of porosity and a film thickness of 76 nm.

It should be appreciated that in some embodiments, the coatings of thepresent disclosure provide an increase in transmission from about 1% toabout 3.5% and in some embodiments from about 1.5% to about 3%, and acontact angle of about 80 degrees to about 120 degrees and in someembodiments about 85 degrees to about 100 degrees.

Typical hardness for a mixture of pure silica sol-gels coatings isobserved to be around 1.05 GPa. Without wishing to be bound by theory,the enhanced mechanical properties of some of the coatings of thisdisclosure (as compared to pure silica-based coatings) may be due toseveral factors that contribute to increased hardness. First, theextensive cross-linking due to the use of the three-precursor systemmakes the Si—O—Si network stronger. Second, the combined use oforganosiloxane and organofluorosiloxane enhances the noncovalentinteractions between the organic side chains to promote betterinteractions that enhance the overall mechanical properties. Third, theincreased interactions between the side chains promote a better fillingof porous void space in the sol-gel network to make a homogenous andlargely nonporous coating. Taken together, the unique combination ofprecursors along with the absence of visible porous microstructure andthe enhanced side chain interactions between the organic groups providesthe improved mechanical properties as compared to coatings of the priorart.

The anti-soiling and self-cleaning property of coatings of thisdisclosure can be tuned by changing the surface characteristics of thesecoatings. XPS data for example coatings of this disclosure show how thefluorine content of the coatings can be varied from 0-9.1% and carboncontent can be varied from 16.8% to 41.7%.

TABLE 12 Showing XPS Data for Coatings of this Disclosure on Tin Side ofTCO Coated Glass Subject to 20 sec Ar+ sputter to remove anyadventitious impurities Sample F % C % Si % O % N % Na % Ca % Example2 + 20 sec 9.1 41.7 16.1 32.1 nd 0.6 0.4 sputter Example 3 + 20 sec nd16.8 28.5 53.6 nd 0.7 0.3 sputter Example 4 + 20 sec 7.4 25.3 21.7 44.10.5 1.0 nd sputter

TABLE 13 Showing XPS Data for Coatings of this Disclosure in the nativestate and after 10 minutes of Argon Sputter Etch on Tin Side of TCOcoated Glass Sample F % C % Si % O % Sn % Na % Ca % Example 2 as 11.939.5 14.9 32.7 nd 0.6 0.4 received Example 2 after 12.9 13.1 28.7 45.10.2 Nd nd 10 min sputter

A comparison of the XPS data for the as received sample from Example 2and the XPS data for the same sample after it is sputtered with Argonions for 10 minutes show that Fluorine from the coating material ispresent in the as received sample and after the 10 minute etch. The dataalso shows that small amount of tin from the tin side of the TCO coatedfloat glass are detected along with the coating.

As indicated elsewhere herein, the coatings of this disclosure may bedeposited on substrates by techniques known in the art, including dipcoating, spraying, drop rolling, or flow coating to form a uniformcoating on the substrate. A flow coating head, as depicted in FIG. 9,FIG. 10, FIG. 11, FIG. 12, FIG. 13, and FIG. 14 may enable improvementsin flow coating. A process for roll coating is described in FIG. 15A,FIG. 15B, and FIG. 16.

FIG. 9 depicts an embodiment of laboratory scale flow coating. Inembodiments, a nozzle (101) dispenses a material (102) onto an inclinedsubstrate (103) as it is moved across the top edge of the substrate. Thematerial flows down the substrate, and the excess drips from the bottomedge of the substrate. The material that remains adhered to thesubstrate undergoes a gelation process as it dries and forms a thin-filmcoating on the substrate.

While the basic laboratory system shown in FIG. 9 can be scaled up insubstrate size, its rate of coating may be slow and wasteful of coatingmaterial. It is possible to recover the coating material that drips offthe bottom edge and recycle it to the nozzle, but this makes control ofcomposition and contamination of the recycled material difficult. Whatis needed is a flow coating system that has a fast coating rate and thatis economical with coating material with minimal wastage dripping fromthe bottom edge, without recycling of this material.

In one embodiment, a coating head such as the one shown in FIG. 13 andin cross-section in FIG. 10 may be used in flow coating. The coatinghead includes a long slot (116) formed between a lower slot manifold(110) and an upper slot manifold (111). This slot is positioned parallelto and extends along the length of the top edge of an inclined substrate(120). In an embodiment, the slot is approximately as long as the edgeof the substrate to be coated. For example, the slot may be orientedalong the longer edge of a rectangular substrate, such that the fluidflows down the substrate along its shorter edge. This orientationminimizes the time required for gravity to carry the fluid across theentire area of the substrate. In an embodiment, a distribution blade(112) bridges the gap between the slot and the top edge of the substratesuch that coating material flowing out of the slot is deposited on tothe distribution blade and then flows under gravity to the bottom of thedistribution blade, which contacts the front surface of the substratejust below the top edge of the substrate. The coating material thenflows off the distribution blade onto the front surface of the substrateand from there down the substrate until eventually it either drips fromthe bottom edge or is removed by other means. The length of thedistribution blade is slightly longer than the length of the slot and ofthe edge of the substrate that is being coated. In an embodiment, thedistribution blade extends beyond each end of the slot manifoldassemblies. For example, the distribution blade may extend 2-100 mmbeyond each end of the slot manifold assemblies. In another example, thedistribution blade may extend 10 mm beyond the substrate.

Coating material is supplied to the slot by a dispensing system, such asa pump (not shown) capable of transferring the liquid coating material,and that is also capable of delivering a measured quantity of coatingmaterial through one or more inlet ports (113) in the lower slotmanifold. The inlet port directs material into a corresponding internalpocket (114) within the lower slot manifold that allows the coatingmaterial to accumulate below the lip of the slot and to spread evenlyalong the slot before it begins to overflow the slot and flow onto thedistribution blade, providing a uniform fluid front of material over theblade. FIG. 12 shows an isometric view of the internal detail of a lowerslot manifold (110). The coating material flows from the port inlet,located in the middle of the internal pocket, outwards toward the endsof the internal pocket and so is distributed evenly along the back sideof the slot lip (140). Once enough material has filled the internalpocket it will begin to overflow the slot lip evenly along the length ofthe slot. The upper slot manifold (not shown in FIG. 12) forms theopposing side of the slot. A seal channel (141) may allow the assemblyto close to the appropriate slot width, as is described herein.

Producing high quality coatings of uniform thickness onto the substratemay depend on the rate at which the fluid flows through the slot. Inturn, the rate at which the material flows may be highly dependent uponseveral factors of the design including the slot length (l), width (w)(152) and height (h) (151), as seen in FIG. 14, the viscosity (μ) anddensity (ρ) of the coating material, and the pressure differential (ΔP)over the width of the slot. In an embodiment, the fluid flow in the slotis both laminar and has a fully developed velocity profile upon exitonto the distribution blade. Laminar flow in the slot can be achieved byensuring the fluid has a Reynolds number less than 1,400. In anembodiment, the Reynolds number (Re) of the coating fluid within theslot is less than 100. The coating fluid may exit the slot with avelocity profile that is independent of subtle edge effects, turbulenceand other disturbances present at the coating fluid's entry into theslot. This condition can be achieved by ensuring the width of the slotis significantly longer than the flow's characteristic entrance length(Le). In an embodiment, the slot width is equal to at least 10 times theentrance length. Such a condition is governed in the following relation,which uses the Blasius approximation to solve for the entrance lengthbetween parallel surfaces:

$L_{e} = \frac{{hRe}_{h}}{100}$

The volumetric rate at which the coating fluid flows through the slot isclosely approximated by the following relation:

$Q = \frac{l\; \Delta \; {Ph}^{3}}{12\; w\; \mu}$

With average flow speed, V, determined by:

$V = \frac{Q}{lh}$

In an embodiment, sol coating flow rates per unit slot length of between5×10⁻⁹ and 5×10⁻⁴ m²/s are useful for coating glass substrates of highquality, and uniform thickness. In an embodiment with a 2 meter longslot, this equates to a volumetric flow rate between 1×10⁻⁷ and 1×10⁻³m³/s. To prevent splatter or turbulent flow or other undesirablephenomena from impacting the distribution blade or substrate, coatingmaterial may not be forced from the slot under high pressure or flowrates. For example, gravity force may be used to drive fluid from theinternal pocket to the distribution blade. In an embodiment, the slot isdesigned such that for the chosen coating material properties, the flowrate out of the slot is less than the flow rate into the internalpocket. This has the effect of building a reservoir of coating materialbehind the slot in the internal pocket, forcing it to spread evenlyunder the influence of gravity along the entire length of the slot andto build up a head height H (150), as in FIG. 14, inside the internalpocket. If the flow rate through the slot is too high, then coatingmaterial will completely flow through part of the slot before spreadingalong the entire length of the slot and reaching the ends furthest awayfrom the inlet port. If the flow rate is too low, then the internalpocket may completely fill with coating material causing an increase inpressure that will create uneven flow rates and excessive back pressureon the coating fluid, and adversely affect the flow rate through theslot. All of these issues can cause the slot flow rate to vary and canaffect the quality and uniformity of the coating. The pressure drop overthe slot width, AP, can be related the fluid head height within theinterior pocket, H (150), the internal pocket pressure Po (154),pressure at the entrance to the narrow slot, P1 (153), and the pressureat the exit of the slot, P2 (155), the fluid material density p and thegravitational constant g according to the following relationship:

ΔP=P ₁ −P ₂

ΔP=ρgH+P _(o)

This pressure input as a function of head height, combined with thedesired flow rate drives the desired slot height, h (151). As a result,careful consideration should be paid to the pressure in the internalpocket. Some embodiments keep the internal pocket sealed via a gasket,o-ring or sealant such that pressure is controlled by the relative flowrates of coating material into and out of the pocket. Other embodimentsmay include vents between the internal pocket and ambient pressure or toan auxiliary pressurization system. In an embodiment, pressure insidethe pocket is vented to the atmosphere and slot height, h, is determinedby the following relationship:

$h = \sqrt[3]{\frac{12\; {Qw}\; \mu}{l\; \rho \; {gH}}}$

Given the above parameters, for a typical sol coating, the width of theslot is between 0.05 and 2 mm, and preferably 0.1 to 0.5 mm. This widthmay be controlled by placing shims between the upper and lower slotmanifolds. Alternative embodiments may use machined steps or other gapcontrol methods. The assembly of upper and lower slot manifolds may havea gasket-like seal along the top and sides to ensure material isdirected towards the slot. An O-ring or similar internal pocket seal mayallow the assembly to close to the appropriate slot width, and may befacilitated with the use of a seal channel (141).

The distribution blade may serve at least three functions in enablingconsistent and uniform coating thickness; 1) it provides a path forcoating material to flow from the slot to the substrate; 2) it has ahigh energy surface that causes the material to spread evenly by surfacetension during its travel from the slot to the substrate; and 3) itprovides an interface to the substrate surface that is tolerant ofimperfections in flatness or warping of the substrate. In oneembodiment, the distribution blade is relatively more flexible than thesubstrate and is able to conform to an uneven or warped substrate. Forexample, the distribution blade is 316 L stainless steel, 2020 mm long,45 mm wide and 0.38 mm thick and the substrate is tempered soda-limeglass 1970 mm long, 984 mm wide and 3.2 mm thick. In another embodiment,the distribution blade is relatively more rigid than the substrate and amechanism clamps the substrate to the back surface such that it is heldflat against the distribution blade. In one embodiment, the distributionblade has a surface energy between 25 mN/m and 100 mN/m.

The coating material exiting the head slot may not naturally form acontinuous curtain or ‘waterfall’ of coating material in the absence ofthe distribution blade, and instead, the coating material may exit theslot with many drips or small rivulets of material all along the lengthof the slot which may not result in a consistent or uniform thicknesscoating on the substrate. To achieve a curtain or “waterfall” out of theslot head in the absence of the distribution blade would requiresignificantly greater flow rates of coating material, and couldtherefore result in significant waste of coating material. Thus, thedistribution blade enables a consistent and uniform thickness coatingwith minimal material waste.

In FIG. 10, the distribution blade is a thin piece of material that isheld in place by a backing plate (118) that along with the distributionblade is attached to the upper slot manifold (111) by a plurality ofbolts or other fastening means (119). This backing plate also serves totension the distribution blade by forcing it forward at a slight angle.This reduces warping of the thin distribution blade along its length.The upper and lower slot manifolds are held together by a plurality ofbolts or other fastening means (117). In some embodiments the bottomedge of the thin distribution blade may be beveled or rounded. In apreferred embodiment it is beveled between 15° and 60°.

In some embodiments the distribution blade is made from a stainlesssteel alloy such as 316 L. In other embodiments it could be made fromtitanium, chrome or nickel plated steel, various corrosion resistantalloys, glass, ceramics, polymer or composite materials such as a metalcoated polymer. The material may be chosen to be chemically resistant tothe composition of the coating material such that it is not damaged bythe coating material and such that it does not contaminate the coatingmaterial in any way.

In FIG. 10, the lower slot manifold has a notch (115) just below theslot. The purpose of this notch is to prevent the flow of coatingmaterial from the slot along the bottom edge of the lower slot manifoldand from there dripping on to the distribution blade or the substrate.

FIG. 11 shows an alternative embodiment of a distribution blade (130)wherein the blade is a solid piece of material that also forms the upperslot manifold. The front surface of the blade (132) acts to distributethe coating material evenly from the slot to the substrate. The bottomedge of the blade is profiled (133) to facilitate the flow of coatingmaterial from the blade onto the substrate. It should be understood thatthe exact shape of this profile can include curved or angled flat bevelsand that the transition of angle from the face of the distribution bladecan range from gradual to abrupt and that the final angle that the edgemakes with the substrate surface can be from 10° (sharp) to 110° degrees(obtuse). In another embodiment, the thick or solid distribution bladedoes not also form the upper slot manifold, but is instead a separatepiece that is bolted onto the slot manifold in a manner similar to thethin distribution blade shown in FIG. 10.

Some embodiments of the distribution blade include coatings or surfacetreatments on the front side (that is the wet side) and on the backside. For example, a front side surface treatment may enhance thespreading of the coating material as it flows to the substrate. Aback-side treatment might repel the coating material to suppressmaterial gathering on the backside due to capillary action that thendripped onto the substrate as it was removed from the distribution orgather on the backside and contaminate the next substrate positionedagainst the blade. Other embodiments of the distribution blade includelaminates and composites where dissimilar materials are fused orassembled together to provide differences between the front and backsidesurface properties as might also be achieved in the case of a coatedmetal blade.

Some embodiments of the coating head manifolds may have coatings orsurface treatments to protect them from adverse chemical reactions withthe coating material or to change how the coating material flows withinthe internal pocket or over the slot lip.

A full coating head may be composed of a plurality of slot manifoldassemblies. For example each slot manifold assembly might be 50 cm long.Four such assemblies may be mounted on a supporting structure such thatthey form a 200 cm long coating head. The dimensions of the slotmanifold assembly and the number of such assemblies used for aparticular length of coating head may be selected to manage the cost ofmanufacturing the slot manifolds themselves and the complexity ofconstructing the coating head from multiple slot manifold assemblies. Inthe case where multiple slot manifold assemblies are used to assemble acoating head, it is advantageous to have a single distribution bladethat is continuous over the entire length of the coating head. However,multiple adjacent or overlapping segments of distribution bladecomprising the length of the coating head are not precluded.

It should be understood that the number of internal pockets and inletports within a slot manifold is variable and may be more or less thanthe two shown in FIG. 12. The number of pockets and inlet ports may beselected to manage the manufacturing complexity of the slot manifold andthe uniformity of flow of coating material from the slot.

In the slot manifold, the wall between internal pockets may be kept asthin as possible. This wall affects the flow of material over the slotlip in its immediate vicinity. By keeping the wall as thin as ispractical, the effect is minimized.

The method of coating using the apparatus may include the followingsteps. First, optionally, the substrate may be prepared for the coatingby increasing the surface energy of the surface to be coated, thusmaking it possible for the coating material to spread evenly on thesubstrate surface by surface tension. In one embodiment, the substrateis glass and the surface energy is increased by washing vigorously withwater and/or mechanical brushes. In other embodiments, the substratesurface may be prepared using gas plasma such as oxygen or by treatmentwith a gas flame. Other pretreatments are described further herein.

Next, the substrate to be coated may be positioned with its top edgealigned with and parallel to the bottom edge of the distribution blade.The bottom edge of the distribution blade may overlap slightly with thetop edge of the substrate. The amount of overlap is dependent upon thecoating requirements but may be at least 0.1 mm and in a preferredembodiment be approximately 3 mm. The ends of the distribution blade mayextend slightly beyond the left and right edges of the substrate,between 2 and 100 mm on each side. In an embodiment, it extends by 10 mmon each side. The substrate may be inclined at an angle of 60° to 85°relative to horizontal. In the case of a flexible thin distributionblade, the angle between the surface of the substrate and the surface ofthe distribution blade may be between 0° and 5°. The substrate can bepushed slightly against the distribution blade to apply pressure to thecontact area such that the distribution blade conforms to any grossirregularity or deviation from flatness of the substrate. In the case ofa rigid distribution blade, the substrate may be positioned with itsfront surface parallel to the back surface of the distribution blade anda clamping mechanism may hold the substrate to the distribution bladesuch that any warping or deviation from flatness of the substrate iseliminated against the flat back side of the distribution blade. In oneembodiment, the coating head is stationary and the substrate is broughtto it. However, in other embodiments, the substrate may be stationaryand the coating head moved to position or both elements may movetogether to arrive at the final coating position. It is also possiblefor both elements to be stationary relative to each other but to bemoving relative to the larger coating system.

Next, the front surface of the substrate may be completely wetted with apre-wet solution. This pre-wet solution is dispensed in a manner thatquickly wets the entire substrate surface rapidly, such as in less than30 seconds. In one embodiment, a plurality of fan nozzles positioned ona rotatable mechanism above and in front of the substrate and along itslength aligned to the coating head starts spraying pre-wet solution suchthat it first wets the distribution blade along it entire length. Thenthe nozzle assembly rotates such that the fan shaped jets of pre-wetsolution from the nozzles travel down the substrate from its top edge toits bottom edge and in the process deposit pre-wet solution on the fullsurface of the distribution blade and the substrate. When employed, thepre-wet step decreases the time for the coating material to completelywet the substrate to between 1 and 25 seconds; improves the uniformityof distribution of the coating material on the substrate to ±25% byvolume per unit area and reduces the amount of coating material neededto completely coat the substrate by up to 90%. The composition of thepre-wet solution is chosen to provide a number of properties: Theviscosity is within ±50% of the viscosity of the coating material andmore preferably within ±10% and even more preferably within ±2% and/orthe surface tension is within ±50% of the surface tension of the coatingmaterial and more preferably within ±10% and even more preferably within±2% and/or the vapor pressure is within ±50% of the vapor pressure ofthe coating material and more preferably within ±10% and even morepreferably within ±2%. In one embodiment, the pre-wet solution comprisesthe same mixture of solvents, mixed in the same ratios as the coatingmaterial. For example, the pre-wet solution might be composed of 90%isopropyl alcohol and 10% water that approximately matches the ratio ofisopropyl alcohol and water in a sol-gel coating material. In analternative embodiment, the pre-wet solution could be a non-ionic,cationic or anionic surfactant, such as for example sodium dodecylsulfate or perfluoroalkyl sulfonate.

Next or some time shortly after the pre-wet step has commenced, apre-determined amount of coating material may be dispensed from thecoating head on to the substrate. The coating material flows down thesubstrate completely covering the front surface of the substrate. Excesscoating material may drip from the bottom edge or be wicked away frombottom edge by capillary action onto a mechanism designed for thatpurpose. In some embodiments, excess coating material may be collectedat the bottom of the substrate for reuse. The decision to reuse thismaterial or not depends on the composition of the coating material andsubstrate. For example, if the coating material is quite stable and doesnot significantly change during the time it travels down the substrateand if the substrate does not contaminate the coating material then adecision might be made to reuse excess material collected from thebottom edge.

Next, optionally, there may be a pause of between 1 and 600 secondsafter the dispensing of coating material has finished while excesscoating material is able to drain out of the internal pocket and fromthe wet surface of the distribution blade onto the substrate. The lengthof this pause may be optimized to reduce the possibility of drips fromthe distribution blade after the substrate is removed from the coatinghead. In some embodiments, this pause may be long enough to allow thedistribution blade and/or the top area of the substrate to dry orpartially dry.

Next, the substrate may be withdrawn from the coating head. In someembodiments, if the coating head is still wet, a drip guard may quicklymove into place between the substrate and the bottom edge of thedistribution blade. This drip guard may optionally touch the bottom edgeof the blade to wick away excess material in which case the surface ofthe drip guard may have similar surface characteristics to the frontsurface of the distribution blade to encourage the coating material toeasily flow off the distribution blade.

Finally, the substrate may be allowed to dry in a manner that allows thecoating material to undergo gelation such that a uniform high qualitycoating is formed on the substrate surface.

This coating method, enabled by the novel design of the coating head canhave several of the following advantages over alternative coatingtechniques. First, by dispensing material simultaneously across the fullwidth of the substrate the time to dispense can be greatly shortened.Second, by pre-wetting the substrate the amount of time for the coatingmaterial to flow down the substrate can be greatly shortened and theamount of coating material required to fully wet the substrate surfaceis greatly reduced. Third, if coating material is not collected at thebottom of the substrate for reuse then only fresh (virgin) material canbe deposited on the substrate so control of coating material purity andcomposition can be greatly increased. Fourth, by utilizing adistribution blade in conjunction with a properly sized slot dispenser,the uniformity of flow of material on to the substrate can be greatlyincreased at very low cost and with a very simply system. Fifth, thetechnique can be very tolerant of deviation of flatness on the substratewithout requiring any precision mechanical control or design. Sixth, themethod does not necessarily pose any significant chemical compatibilitychallenges where it may be difficult to identify critical coatingcomponents with properties that are not sensitive to or contaminate thecoating material. Finally, the method can be inherently single sidedallowing the flexibility to coat one side of the substrate or both (in asecond coating step) if needed.

Is should also be understood that in some embodiments the formulation ofthe coating material will have a significant effect on the uniformity ofthe thin-film. In particular, in a sol-gel coating material the ratio ofsolids or particle content to solvent in conjunction with the ambientconditions during drying may affect the gelation process that occurs asthe thin-film forms. Careful control of these elements will enhance theuniformity of the final thin-film especially in the top to bottomdirection on the substrate.

FIG. 15 a shows a simplified schematic of a forward roll coatingapparatus. FIG. 15 b shows a simplified schematic of a reverseroll-coating apparatus. In both figures, a flat substrate (160) is fedfrom left to right. A counter pressure roller (163) supports thesubstrate from the bottom and moves in a complementary direction to themovement of the substrate. A coating material (164) is deposited in areservoir created between a doctor roller (162) and an applicationroller (161). The pressure or spacing of the doctor roller toapplication roller controls the amount of coating material that istransferred to the application roller. The surfaces of the doctor andapplication rollers may be smooth or textured, soft or hard. The rollersurfaces need not be the same. For example, the doctor roller may becompliant and textured while the application roller could be hard andsmooth and vice versa. The application roller transfers coating materialto the surface of the substrate. The pressure or distance between theapplication roller and the substrate surface is adjustable to facilitatecontrol of the final wet-coating thickness and/or uniformity of thematerial on the substrate. In forward roll-coating, the applicationroller (161) moves in the same direction as the direction of motion ofthe substrate. In reverse roll-coating, the application roller (161)moves in the opposite direction to the motion of the substrate.

The substrate may be continuous, such as for example a roll of polymersheet or steel, or it may be discontinuous, such as discrete pieces ofglass or wood or individual solar modules. In the case of discontinuoussubstrates, the application roller assembly may be moved in a verticaldirection such that it touches down on the leading edge of the substrateas it enters the roll-coater and then lifts off the trailing edge as thesubstrate exits the roll-coater. This technique may reduce uniformity onthe leading and trailing edges.

The selection of the materials within the roll-coater that come intocontact with the liquid coating material are a consideration. In someembodiments, the coating material may be corrosive, having either a highor low pH. In an embodiment, the pH of the coating material is between1.8 and 2.8. Additionally, in some embodiments, the coating materialcontains organic solvents such as iso-propyl alcohol, methanol, ethanol,propanol, propylene glycol monomethyl ether, propylene glycol monomethylether acetate, and the like. All materials may be selected to withstandboth the organic solvents and pH conditions used. For metalliccomponents, stainless steel is preferential with chrome-plated steel,for example. In selecting polymer materials for pipes, fittings andseals made from polytetrafluoroethylene, polypropylene, polyether etherketone, and polyvinylidene difluoride may be considered. For polymercoatings on the rollers polyurethane, EPDM (ethylene propylene dienemonomer) rubber and nitrile rubber are suitable. The particularembodiment of a roll-coater selected for a specific sol-gel coatingapplication depends upon a number of factors. The wet film thickness isa process parameter to consider in achieving the final cured filmthickness. The desired wet thickness may be dependent on the desiredfinal dry thickness, the solids content of the coating material and thetarget porosity of the final dry film. In one embodiment, the desiredfinal thickness is 120 nm (DT), the solids content (SC) of the coatingmaterial is between 1% and 3% by volume and the target porosity (P) is10%. The target wet thickness (WT) may be calculated with the followingformula:

${WT} = \frac{DT}{{SC}*\left( {1 - P} \right)}$

For example, the equation yields a target wet thickness betweenapproximately 4 μm and 14 μm using the input parameters above. Wetthickness can be controlled by a number of process controls on theroll-coater system. Selection of which parameters are most important isdependent upon the characteristics of the coating material, such as forexample its viscosity, and the architecture or operation mode of theroll-coater, such as forward or reverse. Typically, the parametersadjusted are the doctor roller spacing and/or pressure to theapplication roller; the application roller spacing/pressure to thesubstrate; the speed at which the substrate moves and in the case ofreverse roll-coating the difference in speed between the substrate andthe application roller. The speed at which the doctor roller movesrelative to the application roller is also a process parameter. FIG. 16shows an embodiment of a roll-coater used for sol-gel coating of flatsubstrates such as glass or solar modules. The roll-coater (170) ispositioned after a feed-in conveyor (171) and ahead of a feed-outconveyor (172). In FIG. 16, substrates move from right to left. Coatingmaterial (173) is fed to the roll-coater from a storage tank at acontrolled rate by a pump (174). Excess material is collected (177) offthe ends of the rollers and recirculated. An optional pre-heater (175)may be positioned such that it can heat the substrate prior to theroll-coater. The substrate may be heated to a temperature, such as atemperature between 2° C. and 80° C. In some embodiments, this pre-heatstep can serve to reduce thermal stress during the very rapid heating ofsubsequent process step. In other embodiments, it is used to controlevaporation rates of the coating material placed on the substrate toachieve specific process targets such as uniformity, film-thickness,porosity or process speed. Careful consideration should be paidregarding heat transfer from warmed substrates to the application rollersuch that it is accounted for in the process. In one embodiment, aflash-off heater (176) is positioned at the output of the roll-coater tocontrol evaporation of the solvent of the coating material to facilitatethe gelation of the thin-film. In some embodiments, the pre-heater andthe flash-off heater may be radiant infra-red or in other embodimentsthey may be electric or fuel fired convection heaters. In anotherembodiment forced air at ambient or close to ambient temperature couldbe used to accomplish the flash-off process by accelerating solventevaporation.

The conveyor systems used to move substrates between process stages maybe continuous belt driven systems. In some embodiments robots might beused to convey substrates between process stages. In other embodimentsubstrates might be conveyed by humans using carts. In any case itshould be understood that substrates may be conveyed between processsteps by many means known in the art.

An important consideration when using roll-coaters is accommodating orcontrolling for evaporation of coating material solvent from theequipment itself as the machine is running To mitigate this evaporation,it can be advantageous to add make-up solvent to the coating materialsuch that the solids concentration is controlled within a workablerange. Make-up solvent can be added at a constant rate known to matchthe steady-state rate of evaporation; it can be added periodically basedon pre-determined intervals based on time, quantities of substratescoated, or coating material consumed. Make-up solvent can be added basedon an active feedback loop wherein the solids concentration is measureddirectly or indirectly and then used to control the amount added. Solidsconcentration might be measured by optical means such as dynamic lightscattering or adsorption or refractive index; it could be measured byphysical properties such as for example density or viscosity; it couldbe measured chemically such as for example monitoring pH.

Sol-gel materials used for coatings are often sensitive to environmentalconditions such as relative humidity and temperature during the gelationprocess. Additionally, sol-gel materials may release significant amountsof solvent vapor prior to or during cure. It is therefore desirable toengineer the environment around the roll-coating system such as thattemperature and humidity are controlled, and solvent vapor is removed.In some embodiments a containment chamber is built around the completeroll-coater system with a dedicated HVAC unit to control temperature andrelative humidity. In an embodiment, there is a secondary interiorcontainment around the coater application roller and the flash-off areathat is small in volume such that its temperature and relative humiditycan be controlled more easily. This interior containment area is alsoused to collect solvent vapor for venting, destruction or recycling.This has an additional advantage to prevent people working inside theprimary containment area from being subjected to elevated levels ofsolvent vapor. Such an environmental chamber system would have safetyinterlocks such that the tool could be stopped and any coating materialsafely contained if the solvent vapors approached flammability safetylimits.

FIG. 17 shows a cross-sectional schematic view of one embodiment of acuring apparatus and method for skin-cure. In this apparatus, anair-knife (180) directs heated air on to the surface of a substrate(181) presented to the air-knife by a feed-in conveyor (182) andextracted by a feed-out conveyor (183). The air may be heated by anelectrical element (184), as shown in FIG. 17, may also be heated by anyother method known in the art. The air may be heated to any temperatureuseful in the method, such as to a temperature of 300° C. to 1000° C.Air may be forced through the heating element and air-knife by a fan(185). The temperature of the air is controlled by an electroniccontroller (186) and temperature sensor (188) located in the heated airstream. Optionally, overheat protection of the heating element may beprovided by the electronic controller and, optionally, a secondtemperature sensor (187) located close to the heating element. When nosubstrate is present, air may flow from the fan through the heatingelement, through the air-knife and then directly to the exhaust (197).When a substrate is present, the air flows along the top surface of thesubstrate. In an embodiment, a pre-heating stage (189), for example aninfra-red emitter, heats the substrate prior to the air-knife. Thepre-heat temperature is controlled by an electronic controller (190) anda temperature sensor (191) with an optional safety over-heat sensor(192). In another embodiment, a flat plate attached to the leading edgeof the air-knife forms a pre-heat chamber (189) with the top surface ofsubstrate. This pre-heat chamber traps the hot air close to thesubstrate surface for a longer period allowing the hot air more time topre-heat the substrate surface. A post-heating stage (193), for examplean infra-red emitter (190) located subsequent to the air-knife providesadditional heat that can extend the time that the substrate stays at anelevated temperature. The post-heating temperature is controlled by anelectronic controller (194) and a temperature sensor (195), with anoptional safety over-heat sensor (196). In another embodiment, there isa heating element in place of the pre-heat chamber. The pre-heating ofthe substrate can serve to reduce thermal stress during the very rapidheating under the air-knife and to provide an additional control on thepeak temperature the substrate reaches under the air-knife, the peaktemperature being a function of the initial temperature plus thetemperature rise due to the air-knife.

A major advantage of this embodiment of a skin-cure system is that itallows the curing of a thin-film sol-gel coating without heating theentire substrate to a high temperature. A properly configured air-knifeis able to heat the surface very fast (high power) without imparting agreat deal of heat (energy) to the full substrate. Thus while thesurface heats rapidly to a high temperature the overall substrate doesnot heat up excessively. In one embodiment the substrate is glass coatedon one side with thin-film solar cells, and the opposing side of theglass is the desired surface for the sol coating. In this case, it isdesirable to avoid heating and raising the temperature of thesemiconductor photovoltaic material as much as possible while curing thesol coating. Thin-film solar materials such as CdTe, CIGS or amorphoussilicon can be quite sensitive to elevated temperatures. Hightemperatures can cause dopants within the material to defuse in adetrimental manner or can cause metal electrode materials to defuse intothe photovoltaic material. In some embodiments, the temperature of thephotovoltaic cell may be kept from exceeding 100° C. to 120° C. as thesol is cured. Additionally, polymer materials within the finished solarmodule such as encapsulates may be kept from exceeding their glasstransition temperature of 150° C. to 200° C.

FIG. 10 shows an example temperature profile for a skin-cure system. Inthis example the substrate is a dummy thin-film solar module consistingof two pieces of glass typical of those used in thin-film modulemanufacturing, laminated together with temperature sensors embeddedbetween the glass sheets such that they measure the interior temperatureof the dummy module and temperature sensors attached to the top surface.The module is moved at a speed of 1 cm/s under an air-knife set to anexit air temperature of approximately 650° C. and a gap distance (fromsubstrate top surface to the air-knife opening) of approximately 1 cm.Two temperatures are shown, the top surface temperature representing thetemperature reached by the interior of the dummy module. In this examplethe pre-heat chamber embodiment was used. From the profile, the pre-heatchamber caused an initial rise in temperature of the top surface (202)to approximately 100° C., there after the air-knife caused a very rapidtemperature rise (200) to approximately 300° C. after which thepost-heat infra-red emitter set to a temperature of 300° C. as measuredby a sensor placed between the substrate and the IR emitter, maintainsthe top surface temperature (201) at approximately 200° C. Through-outthe process the interior temperature never exceeds approximately 90° C.

In one embodiment, the substrate is glass of thickness 1 mm to 4 mm. Inan embodiment of a skin-cure apparatus, the air-temperature exiting theair knife is between 500° C. to 750° C. as controlled by the powersetting of the heating element and the volume of air provided by thefan. The speed of the substrate is between 0.25 cm/s and 3.5 cm/s. Theresulting temperature of the substrate surface is between 150° C. to600° C. and this temperature is attained between the start of thepre-heat chamber and the end of the air-knife In other embodiments thesubstrate is pre-heated by an infra-red emitter to approximately 25° C.to 200° C. prior to the air-knife wherein it is further heated toapproximately 150° C. to 600° C. Thereafter, the substrate is maintainedat a temperature of between 120° C. to 400° C. until the end of thepost-heat section. Such a configuration of the skin-cure apparatus hasbeen shown to cure the sol coating while leaving the opposing surface ata temperature below 120° C.

The process of rapidly heating the substrate using the air-knife andthen maintaining that temperature with radiant heat facilitates thecuring of the sol-gel material. In an embodiment, the curing is achievedby providing sufficient energy so that a sufficient portion of theremaining Si-moieties within the coating undergo a condensation reactionand form Si—O—Si crosslinks that greatly strengthen the materialenabling it to pass Taber abrasion testing to standard EN1096.2 with nomore than 0.5% loss of absolute transmission. In other embodiments, thecuring temperature is used to facilitate other processes such asvolatizing a sacrificial component of the coating to form a desiredporosity or a desired surface morphology. Other embodiments may use veryhigh temperatures to completely oxidize all organic components in thecoating creating a hydrophilic pure silica film. Yet further embodimentsmay use the heat and/or reactive gas composition of the air-knife toinitiate chemical reactions that modify the properties of the coating,such as for example, surface energy, color, refractive index, surfacemorphology and surface chemistry. In embodiments, the skin-cure processworks in concert with the composition and properties of the coatingmaterial to facilitate tuning of the properties of the final thin-filmcoating.

FIG. 19 shows a thermogravimetric analysis of representative samples ofcoating material. Thermogravimetric analysis is performed by heating asample gradually and recording the loss of mass as various components ofthe sample volatize. When performed on coating materials such as theseexample sol-gel coatings for glass, it can be used to determine criticaltemperatures required to cure the coating material. The figure showsthree temperatures of interest. Using Sample 1 from example 3 in FIG. 19as an illustrative example, there is a point of inflection (210) atapproximately 125° C., another much steeper point of inflection (211) atapproximately 450° C. finally there is a flattening out (212) above 500°C. Without being bound by theory, these three points are interpreted asfollows. As temperature increases to point 210 any residual water andsolvent is volatilized and all easily accessible Si—OH moieties react,condense and release water. This represents a cured film that hasattained a useful hardness and abrasion resistance at a relatively lowtemperature. Further heating in the range from point 210 until point 211represents an approximately linear reduction in mass as additionalremaining Si—OH moieties condense and release water. This temperaturerange represents increasing hardness and abrasion resistance of thematerial with increasing temperature, without detrimental effects on thecoating. This reduction in mass causes a corresponding decrease indensity and hence a decrease in refractive index. In coating materialsthat form hydrophobic films, the reduction in Si—OH will also result inan increase of the hydrophobic effect as measured by increasing watercontact angle. Heating beyond point 211 begins to oxidize organicmoieties within the coating and decomposes the material, the byproductsof which may then volatilize. In some embodiments these moieties may bemethyl groups or other hydro-carbon groups or fluoro-carbon chains orany combination thereof. Other reactions may also occur such as forexample the formation of SiC and Si_(x)O_(y)C_(z). This temperatureregime may be generalized as the oxidation of the organic components ofthe coating, reactions between byproducts of that oxidation with eachother and with components of the film itself and the transformation ofthe coating to a substantially inorganic silica coating. At this pointfurther heating no longer causes significant mass loss and the curveflattens out as indicated by point 212. Sample 2 of example 2 exhibitsapproximately the same shape and inflection points as Sample 1. It alsoillustrates that when more complex organic moieties are present in thecoating the transformation that occurs after the second inflection pointcan be more complex and more prolonged. Therefore for the purposes ofdeveloping a process for curing these coatings we can determine fromthis analysis that a first low temperature cure can be accomplished at atemperature of approximately 125° C., which is the first point ofinflection. A second higher temperature cure at the second point ofinflection (approximately 450° C. for the material in Sample 1 and 350°C. for the material in Sample 2) results in increased hardness, abrasionresistance and hydrophobicity. Temperatures beyond the second inflectionpoint result in the breakdown and modification of organic moieties thatmay in some embodiments be useful.

The curing process parameters including substrate speed, air knifeoutput air temperature, air knife air flow volume, air knife openingdistance to substrate surface, pre and post heating set temperatures areused to control process cure parameters including maximum temperature,rate of heating, duration at temperature, cumulative temperatureexposure and rate of cooling that can be used to tune specificproperties of the final cured film. One property is hardness as measuredby nanoindentation methods. In some embodiments, the curing systemdescribed herein may cure sol-gel coatings on glass substrates to ahardness of approximately 0.2 GPa to 10 GPa and preferably to a hardnessof approximately 2 GPa to 4 GPa. Another property is abrasionresistance. In some embodiments, the curing system described herein maycure sol-gel coatings on glass substrates to an abrasion resistancewhereby they lose no more than 1% of absolute optical transmission asmeasured by spectrophotometer after 500 strokes of an abrasion testperformed in accordance with specification EN1096.2 and preferably nomore than 0.5% loss of absolute optical transmission after 1000 strokes.Such a test can be performed using a Taber reciprocating abrader model5900 with a ratcheting arm assembly. A third property is surface energyas measured by water contact angle (WCA). In some embodiments the curingsystem described herein may cure sol-gel coatings to a WCA ofapproximately 60° to 120° and preferably to a WCA of approximately 70°to 100°. In other embodiments the film can be cured to a WCA ofapproximately 5° to 30° and preferably a WCA of approximately 10° to20°. A fourth property is refractive index (RI) as measured byellipsometer. In some embodiments curing system described herein maycure sol-gel coatings to a RI of approximately 1.25 to 1.45 andpreferably a RI of approximately 1.35 to 1.42. A fifth property is finalfilm thickness as measured by ellipsometer. The final film thickness isa function of the initial (pre-cure) dry film thickness and the cureparameters such that the cure parameters modify the initial drythickness. In some embodiments the curing system described herein maycure sol-gel coatings to a thickness of 50 nm to 150 nm and to apreferred thickness of 70 nm to 130 nm.

FIGS. 20 a, 20 b and 20 c depict data for an exemplary sol-gel coatingthat demonstrate control of final film thickness, refractive index andwater contact angle as a function of maximum cure temperature.

FIG. 20 d shows Fourier transform infrared spectra (FT-IR) of sol-gelcoating material from example 3 taken before and after a cure processstep. This analysis technique shows how chemical bonds within thematerial change during the curing process. In particular the spectralpeaks denoted by points 220, 221 & 222 have changed during the process.Without being bound by theory, these changes can be interpreted as thereduction of Si—OH bonds through condensation causing the reduction ofthe peaks at points 220 and 222. These bonds are converted to Si—O—Sibonds causing the increase in the peak at point 221. This analysistechnique can be used to quantify the proportion of Si—OH bonds thatcondense and hence to quantify the degree to which the film is cured.FIG. 20 e shows FT—IR spectra of example 3 cured at different curetemperatures of 120° C., 200° C. and 400° C. FIG. 20F shows FT-IRspectra of example 2 before and after cure.

FIG.21 shows Si-29 NMR of the sol from example 2 taken before coatingand curing. The assigned chemical shifts and qualitative mol % of totalmolecules are shown in the table 14.

TABLE 14 The list of assigned peaks and % of total molecules in FIG. 21.% of unit in the total sol Si signal in unit Structure Chemicalshifts/ppm structure [RSi(OH)₂O_(0.5)]_(a) 53 8 [RSi(OH)O]_(c) 58 9[RSiO_(1.5)]_(b) 63.3 40.49 [Si(OH)₃O_(0.5)]_(z) 90 9.85 [Si(OH)₂O]_(y)93 4.73 [Si(OH)O_(1.5)]_(y) 99.65 27.21 [SiO₂]_(x) 108.52 10.42Total Si—OH containing units in the sol of example 3 is 58.79 mol % ofunits of the total sol structure based in Si—NMR. However, not all Si—OHhave the same reactivity towards condensation as some have more sterichindrance than others in the complex cage, branch and network structureof the sol polymer.

FIG.22 shows Si-29 NMR of the sol from example 3 taken before coatingand curing. The assigned chemical shifts and qualitative mol % of totalmolecules are shown in the table 15.

TABLE 15 The list of assigned peaks and % of total molecules in FIG. 22.% of unit in the total sol Si signal in unit Structure Chemicalshifts/ppm structure [RSi(OH)₂O_(0.5)]_(a) 53 11.11 [RSi(OH)O]_(c) 581.00 [RSiO_(1.5)]_(b) 63.3 41.38 [Si(OH)₃O_(0.5)]_(z) 90 11.4[Si(OH)₂O]_(y) 93 4.73 [Si(OH)O_(1.5)]_(y) 99.65 30.27 [SiO₂]_(x) 108.5211.74Total Si—OH containing units in the sol of example 3 is 58.81 mol % ofunits of the total sol structure based in Si-NMR. However, not all Si—OHhave the same reactivity towards condensation as some have more sterichindrance than others in the complex cage, branch and network structureof the sol polymer.

Coated samples of examples 11-34 were cured at various conditions. Filmthickness, refractive index (RI), solar spectrum weighted transmissiondelta (ΔT_(AM)), and abrasion loss according to tests described hereinbased on European Standard EN1096.2 (Glass in Building, Coated Glass)were measured and summarized in the Table 16.

The T_(AM) metric is solar weighted transmission using the IS060904solar spectrum between 380 nm to 1100 nm. ΔT_(Am) is the difference insolar weighted transmission between a coated sample of glass and anuncoated sample of the same type of glass.

TABLE 16 Cure conditions, metrology and performance results of coatingsfrom examples 11-34. Cure Cure Temperature Time Thickness AbrasionExample # (° C.) (min) (nm) RI ΔT_(AM) P/F 11 500 30 135.30 1.258 3.22 P12 500 30 120.40 1.289 2.99 P 13 500 30 126.20 1.325 2.75 P 14 500 30120.53 1.260 3.34 P 14 Tempered 124.43 1.280 3.04 P 16 500 30 127.301.260 3.23 P 17 500 30 103.70 1.290 2.84 P 18 300 60 131.09 1.340 2.56 P19 500 30 129.33 1.280 3.07 P 20 300 30 142.90 1.340 2.45 F 21 300 30154.80 1.290 2.76 P 22 550 15 147.10 1.260 3.14 P 23 550 15 121.63 1.2902.98 P 24 550 15 133.20 1.270 3.18 P 25 300 30 136.27 1.360 2.13 F 26300 30 162.10 1.313 2.49 F 27 300 15 133.85 1.288 2.91 F 28 300 15124.13 1.290 3.00 F 29 300 15 130.00 1.311 2.89 P 30 300 15 135.97 1.3162.91 P 31 300 30 127.30 1.341 2.50 N/A 32 550 15  89.20 1.383 1.48 P 33300 30 105.23 1.387 1.80 P 34 550 15 125.78 1.307 3.05 NA

The coating and curing process steps may further be configured to createcoatings of varying complexity and structure. In embodiments, anycombination of coating technique and curing technique may be used toachieve a final coating for a substrate. Embodiments of suchcombinations may include coating via a flow coating technique followedby a skin cure process or cure by conventional means, coating via a rollcoating technique followed by a skin cure process or cure byconventional means, and the like. To generate multilayer coatings, anycombination of coating and curing apparatus may be used sequentially togenerate such a coating. The sequential use of such apparatus may beenabled by an arrangement that places multiple coating apparatus andcuring apparatus in sequence. Alternatively, handling facilities mayexist for handling the substrate between one or more coating and curingapparatus. For example, two roll-coaters may be placed in sequence withan optional flash-off heater in between. This facilitates coating of afirst layer by the first roll-coater, drying of the layer by theflash-off station, then deposition of a second layer by the secondroll-coater before curing in a skin-cure station or in a simple oven.Alternatively, a high temperature skin-cure step may be interposedbetween the roll-coaters to enable a high temperature heat treatment tothe first layer before application of the second layer. It is understoodthat this technique for multiple layer coatings may be extended to morethan two layers. Multi-layer coatings manufactured by this technique maybe high performance anti-reflective interference type coatings ormultiple layers coatings could be used to modify the surface energy ofthe top surface coating by for example adding a fluorinated silanemono-layer to an underlying layer to make the final coating hydrophobicand oleophobic on the environmentally exposed surface. The multi-layercoatings may be used to enhance single layer anti-reflective coatings byadding a lower refractive index material on the environmentally exposedsurface to create a graded index coating between the environment and theunderlying substrate. In embodiments, a second layer of coating may beapplied to an existing base layer to provide a functional benefit of themulti-layer coating in combination with the base layer. For example, amobile phone/touch screen glass may be coated with an inorganic coatingthat provides anti-scratch benefits, then a low-temperature anti-soilingcoating may be on top of the anti-scratch coating.

The foregoing apparatus and methods are particularly well suited to theapplication of sol-gel thin-films to glass. In an embodiment, the glassto be coated is the front (sun facing) surface of a solar module and thesol-gel thin-film is an anti-reflective coating. Either bare glass maybe coated and/or cured by the apparatus or fully assembled solar modulesor solar modules at any intermediate stage of manufacture. In otherembodiments, the apparatus may be used to coat and/or cure windows,architectural glass, displays, lenses, mirrors or other electronicdevices.

In an aspect, a coating and curing apparatus may include a conveyorsystem of a combination roll coating and curing facility, wherein thecombination roll coating and curing facility comprises at least one rollcoating facility and at least one curing facility, and wherein theconveyor system is adapted to transport a substantially flat substratethrough the combination roll coating and curing facility, a processorthat controls a process parameter of the at least one roll coatingfacility, and an air knife of the at least one curing facility, whereinthe air knife is adapted to direct heated air to a portion of the flatsubstrate as it is transported through the at least one curing facility,wherein the at least one roll coating facility is adapted to coat thesubstantially flat substrate with a sol gel coating material. Thesubstantially flat substrate may be a part of at least a partiallyfinished solar module. The apparatus may further include an electricalelement disposed within the air stream to heat the air flowing throughthe air knife The air may be heated to a temperature between about 300°C. and 1000° C. The apparatus may further include a fan in the airstream that directs air to the air-knife. The apparatus may furtherinclude an electronic controller that controls the temperature based onreadings from at least one temperature sensor located in the air stream.The apparatus may further include an exhaust to remove heated air fromthe apparatus. The apparatus may further include a flat plate attachedto the leading edge of the air-knife, wherein the flat plate is adaptedto form a pre-heat chamber with the top surface of the substantiallyflat substrate. The apparatus may further include an infra-red emitterdisposed along the conveyor system prior to the air knife, wherein theinfra-red emitter is adapted to heat the substantially flat substrate toa temperature of between 25° C. to 200° C. The apparatus may furtherinclude an infra-red emitter disposed along the conveyor systemsubsequent to the air knife, wherein the infra-red emitter is adapted tomaintain the flat substrate at a temperature of between 120° C. to 400°C. The process parameters may include at least one of a doctor rollerspacing and/or pressure to an application roller, the application rollerspacing or pressure taken with respect to the substantially flatsubstrate, a speed at which the substantially flat substrate is conveyedby the conveyor system, and in the case of reverse roll-coating, adifference in speed between the substantially flat substrate and theapplication surface of the application roller. The processor may furthercontrol a process parameter of the curing facility. A plurality of rollcoating facilities and curing facilities may be arranged sequentially.The air-temperature exiting the air knife may be between 500° C. to 750°C. The speed of the substantially flat substrate on the conveyor systemmay be between 0.25 cm/s and 3.5 cm/s. The resulting temperature of asurface of the substantially flat substrate may be between 150° C. to600° C.

In an aspect, a method of coating and curing may include conveying asubstantially flat substrate to be coated with a conveyor system througha combination roll coating and curing facility, wherein the combinationroll coating and curing facility comprises at least one roll coatingfacility and at least one curing facility, roll coating thesubstantially flat substrate with a sol gel coating material with the atleast one roll coating facility, and curing the sol gel coating materialon the substantially flat substrate with an air knife of the at leastone curing facility, wherein the air knife is adapted to direct heatedair to a portion of the substantially flat substrate as it istransported through the curing facility by the conveyor system. Asol-gel coated substantially flat substrate may be formed by the method,wherein a portion of the sol-gel coating material is cured while adifferent portion of the sol-gel coating material remains uncured.

In an aspect, a method of tuning the performance of a sol gel coatingmay include determining a desired cure temperature profile to achieve aspecific performance metric for a sol gel coating using at least onephysical analysis method, selecting settings for an air knife curingsystem's operating parameters to achieve the desired temperatureprofiles for the sol gel coating on a substantially flat substrate, andcuring the sol-gel coating on the substantially flat substrate with theair knife curing system. The at least one physical analysis method mayinclude at least one of thermogravimetric analysis, Fourier transforminfrared spectroscopy, ellipsometry, nanoindentation, abrasion testing,spectrophotometry, and a water contact angle measurement. The air knifecuring system operating parameters may include at least one of substratespeed, air knife air-flow volume, air knife output air temperature, airknife opening distance to substrate surface, a temperature set-point fora pre-heating zone and a temperature set point for a post heating zone.The performance metric for the sol-gel coating may include at least oneof hardness, abrasion resistance, surface energy, refractive index,optical transmission, thickness and porosity. The method may furtherinclude a step of coating the substantially flat substrate with the solgel coating using a roll-coating system before the step of curing. Asol-gel coated substantially flat substrate may be formed by the method.The specific performance metric may include a hardness of the sol-gelcoating within a range of 0.2 GPa to 10 GPa. The specific performancemetric may include a test in which no more than 1% of absolute opticaltransmission is lost after at least 500 strokes of an abrasion testperformed in accordance with specification EN1096.2. The specificperformance metric may include a water contact angle where the watercontact angle is within 60° to 120°. The specific performance metric mayinclude a water contact angle where the water contact angle is within 5°to 30°. The specific performance metric may include a refractive indexof the cured, coated sol gel from 1.25 to 1.45. The thickness may beapproximately 50 nm to 150 nm. A sacrificial component of the sol-gelcoating may be volatilized to form a desired porosity.

It should be appreciated that reference throughout this specification to“one embodiment” or “an embodiment” means that a particular feature,structure or characteristic described in connection with the embodimentis included in at least one embodiment of the present disclosure.Therefore, it is emphasized and should be appreciated that two or morereferences to “an embodiment” or “one embodiment” or “an alternativeembodiment” in various portions of this specification are notnecessarily all referring to the same embodiment. Furthermore, theparticular features, structures or characteristics may be combined assuitable in one or more embodiments of the disclosure.

Similarly, it should be appreciated that in the foregoing description ofexemplary embodiments of the disclosure, various features of thedisclosure are sometimes grouped together in a single embodiment,figure, or description thereof for the purpose of streamlining thedisclosure aiding in the understanding of one or more of the variousinventive aspects. This method of disclosure, however, is not to beinterpreted as reflecting an intention that the claimed disclosurerequires more features than are expressly recited in each claim. Rather,as the following claims reflect, inventive aspects lie in less than allfeatures of a single foregoing disclosed embodiment. Thus, the claimsfollowing the detailed description are hereby expressly incorporatedinto this detailed description, with each claim standing on its own as aseparate embodiment of this disclosure.

While the disclosure has been disclosed in connection with the preferredembodiments shown and described in detail, various modifications andimprovements thereon will become readily apparent to those skilled inthe art. Accordingly, the spirit and scope of the present disclosure isnot to be limited by the foregoing examples, but is to be understood inthe broadest sense allowable by law.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the disclosure (especially in the context of thefollowing claims) is to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the disclosureand does not pose a limitation on the scope of the disclosure unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe disclosure.

While the foregoing written description enables one of ordinary skill tomake and use what is considered presently to be the best mode thereof,those of ordinary skill will understand and appreciate the existence ofvariations, combinations, and equivalents of the specific embodiment,method, and examples herein. The disclosure should therefore not belimited by the above described embodiment, method, and examples, but byall embodiments and methods within the scope and spirit of thedisclosure.

All documents mentioned herein are hereby incorporated in their entiretyby reference. References to items in the singular should be understoodto include items in the plural, and vice versa, unless explicitly statedotherwise or clear from the text. Grammatical conjunctions are intendedto express any and all disjunctive and conjunctive combinations ofconjoined clauses, sentences, words, and the like, unless otherwisestated or clear from the context.

1. A siloxane polymer solution composition, comprising: (i) a siloxanepolymer A formed from an acid hydrolyzed alkoxysilane, an acidhydrolyzed organosilane, and optionally an acid hydrolyzedorganofluorosilane, wherein the acid hydrolyzed organosilane and theoptional acid hydrolyzed organofluorosilane are each separately preparedbefore combining with another reagent, wherein the siloxane polymer Ahas the following formula:[RSi(OH)₂O_(0.5)]_(a)[RSiO_(1.5)]_(b)[RSi(OH)O]_(c)[R′Si(OH)₂O_(0.5)]_(m)[R′SiO_(1.5)]_(n)[R′Si(OH)O]_(p)[SiO2]_(w)[Si(OH)O_(1.5)]_(x)[Si(OH)₂O]_(y)[Si(OH)₃O_(0.5)]_(z),where R is selected from the group consisting of independently methyl oroptionally substituted or unsubstituted C2 to C 10 alkyl group, asubstituted or unsubstituted C3 to C20 cycloalkyl group, a substitutedor unsubstituted C1 to C 10 hydroxyalkyl group, a substituted orunsubstituted C6 to C20 aryl group, a substituted or unsubstituted C2 toC20 heteroaryl group, a substituted or unsubstituted C2 to C 10 alkenylgroup, a substituted or unsubstituted carboxyl group, a substituted orunsubstituted (meth)acryl group a substituted or unsubstitutedglycidylether group, or a combination thereof, R′ is selected from thegroup consisting of a fluorine substituted C3 alkyl group or optionallyC4 to C10 alkyl group, a fluorine substituted C3 to C20 cycloalkylgroup, a fluorine substituted C1 to C10 hydroxyalkyl group, a fluorinesubstituted aryl group, a fluorine substituted C2 to C20 heteroarylgroup, a fluorine substituted C2 to C 10 alkenyl group, a fluorinesubstituted carboxyl group, a substituted or unsubstituted (meth)acrylgroup, a fluorine substituted glycidylether group, or a combinationthereof, 0<a,b,c,w,x,y,z<0.9, 0≦m,n,p<0.9, a+b+c+m+n+p+w+x+y+z=1; and(ii) a hydrolysis acid catalyst; a polar organic solvent; and at leastone of a porogen; a template; a basic Si—OH condensation catalyst; and asurfactant.
 2. The composition of claim 1, wherein said siloxane polymerA comprises a weight average molecular weight (Mw) of 600 to 10,000Daltons.
 3. The composition of claiml, wherein said siloxane polymer Acomprises 0.1 to 10 weight percent of the total weight of the sol. 4.The composition of claim 1, wherein said alkoxysilane comprisestetramethoxysilane, said organosilane comprises methyltrimethoxysilane,and said organofluorosilane comprises trifluoropropyltrimethoxysilane.5. The composition of claim 1, wherein said alkoxysilane comprisestetraethoxysilane, said organosilane comprises methyltrimethoxysilane,and said organofluorosilane comprises trifluoropropyltrimethoxysilane.6. The composition of claim 1, wherein said alkoxysilane comprisestetramethoxysilane, said organosilane comprises methyltrimethoxysilane,and said organofluorosilane comprises(tridecafluoro-1,1,2,2-tetrahydrooctyl)trimethoxysilane.
 7. Thecomposition of claim 1, wherein said alkoxysilane comprisestetraethoxysilane, said organosilane comprises methyltrimethoxysilane,and said organofluorosilane comprises(tridecafluoro-1,1,2,2-tetrahydrooctyl)trimethoxysilane.
 8. Thecomposition as of claim 1, wherein said siloxane polymer A comprises arelative weight ratio of said tetraalkoxysilane to a total of saidorganosilane and said organofluorosilane of 0.2 to
 2. 9. The compositionof claim 1, wherein the hydrolysis acid catalyst is selected from thegroup consisting of hydrochloric acid, nitric acid, sulfuric acid,phosphoric acid, boric acid, methanesulfonic acid or acetic acid inamount of 0.01 to 1.0 weight present of the total sol formulation. 10.The composition of claim 1, wherein the polar organic solvent isselected from the group consisting of alcohols, esters, ethers,aldehydes, and ketones; and water, wherein an amount of the amount ofsaid solvent and said water in said mixture is from 50% to 99.5% byweight.
 11. The composition of claim 1, wherein the porogen and thetemplate is selected from the group consisting of ethylene oxide,propylene oxide, polyethylene oxides, polypropylene oxides, ethyleneoxide/propylene oxide block co-polymers, polyoxyethylatedpolyoxypropylated glycols, fatty acid ethoxylates, ethylene glycolesters, glycerol esters, mono-di-glycerides, glycerylesters,polyethylene glycolesters, polyglycerol esters, polyglyceryl esters,polyol monoesters, polypropylene glycol esters, polyoxyalkylene glycolesters, polyoxyalkylene propylene glycol esters, polyoxyalkylene polyolesters, polyoxyalkylene glyceride esters, polyoxyalkylene fatty acid,sorbitan esters, sorbitan fatty acid esters, sorbitan esters,polyoxyalkylene sorbitan esters, polyoxyethylene sorbitan monolaurate,polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitantristearate, and sorbitan ester ethoxylates in an amount of 0.1 to 5 wt% of total sol composition.
 12. The composition of claim 27, wherein thenanofiller is selected from the group consisting of colloidal silica,hollow silica nanospheres, polymer beads, polylactic acid,polyvinylpyrrolidone, polymethylmethactrylates and polyacrylates, carbonnanotubes, or Buckminsterfullerene C₆₀-C₇₀ in an amount of 0.1 to 5.0 wt% of the total sol formulation.
 13. The composition of claim 27, whereinthe adhesion promoter is selected from the group consisting of(meth)acryloxypropyl trimethoxysilane, (meth)acryloxypropyltriethoxysilane, (meth)acryloxypropyl dimethylmethoxysilane,(meth)acryloxypropyl methyldimethoxysilane, 3-glycidylpropyltrimethoxysilane, 3-glycidylpropyl triethoxysilane, 3-glycidylpropyldimethylmethoxysilane, or 3-glycidylpropyl methyldimethoxysilane in anamount of 0.1-5.0 weight percent of the total sol formulation.
 14. Thecomposition of claim 1, wherein the basic Si—OH condensation catalyst isselected from the group consisting of a hydroxide selected from thegroup consisting of potassium hydroxide (KOH), sodium hydroxide (NaOH),cesium hydroxide (CsOH) and tetramethyl ammonium hydroxide (TMAH); anamide selected from the group consisting of formamide, dimethylformamide(DMF) and N,N-dimethyl acetamide (DMA); imidazolines, an amine selectedfrom the group consisting of ammonium hydroxide (NH₄OH), triethyl amineand trimethyl amine; N-methylpyrrolidinone (NMP); and tetramethoxymethylglycoluril (PowderLink 1174) in an amount of 0.1 to 1.0 wt % of thetotal sol formulation.
 15. The composition of claim 1, wherein thesurfactant is selected from the group consisting of nonionicsurfactants, polyoxyethylene glycol alkyl ethers (Brij 58),polyoxyethylene octyl phenyl ether (TX-100), polyoxyethylene glycolsorbitan alkyl esters (polysorbate), ionic surfactants,cetyltrimethylammonium bromide and other tetraalkylammonium halides inan amount of 0.1 to 5.0 wt % of the total sol formulation.
 16. Thecomposition of claim 1, wherein the siloxane polymer contains 10 to 50mol % Si—OH groups as established by Si—NMR.
 17. A method of forming acoating on a glass substrate, comprising: preparing a siloxane polymersolution composition, comprising: a siloxane polymer A formed from anacid hydrolyzed alkoxysilane, an acid hydrolyzed organosilane, andoptionally an acid hydrolyzed organofluorosilane, wherein the acidhydrolyzed organosilane and the optional acid hydrolyzedorganofluorosilane are each separately prepared before combining witheach other and with a reagent, wherein the siloxane polymer A has thefollowing formula:[RSi(OH)₂O_(0.5)]_(a)[RSiO_(1.5)]_(b)[RSi(OH)O]_(c)[R′Si(OH)₂O_(0.5)]_(m)[R′SiO_(1.5)]_(n)[R′Si(OH)O]_(p)[SiO2]_(w)[Si(OH)O_(1.5)]_(x)[Si(OH)₂O]_(y)[Si(OH)₃O_(0.5)]_(z), where Ris selected from the group consisting of independently methyl oroptionally substituted or unsubstituted C2 to C 10 alkyl group, asubstituted or unsubstituted C3 to C20 cycloalkyl group, a substitutedor unsubstituted C1 to C10 hydroxyalkyl group, a substituted orunsubstituted C6 to C20 aryl group, a substituted or unsubstituted C2 toC20 heteroaryl group, a substituted or unsubstituted C2 to C10 alkenylgroup, a substituted or unsubstituted carboxyl group, a substituted orunsubstituted (meth)acryl group a substituted or unsubstitutedglycidylether group, or a combination thereof, R′ is selected from thegroup consisting of a fluorine substituted C3 alkyl group or optionallyC4 to C10 alkyl group, a fluorine substituted C3 to C20 cycloalkylgroup, a fluorine substituted C1 to C10 hydroxyalkyl group, a fluorinesubstituted aryl group, a fluorine substituted C2 to C20 heteroarylgroup, a fluorine substituted C2 to C10 alkenyl group, a fluorinesubstituted carboxyl group, a substituted or unsubstituted (meth)acrylgroup, a fluorine substituted glycidylether group, or a combinationthereof, 0<a,b,c,w,x,y,z<0.9, 0≦m,n,p<0.9, and a+b+c+m+n+p+w+x+y+z=1;the siloxane polymer composition further comprising a hydrolysis acidcatalyst; a polar organic solvent; and at least one additive selectedfrom the group consisting of: a porogen; a template; a basic Si—OHcondensation catalyst; and a surfactant; and coating the solar glass orglass module with the siloxane polymer solution; and curing the coatingto form a thin film.
 18. The method of claim 17, wherein the siloxanepolymer solution is prepared in a two-step process comprising preparinghydrolyzed organosilane before combining with an alkoxysilane.
 19. Themethod of claim 17, wherein the siloxane polymer solution is prepared ina two-step process comprising preparing hydrolyzed alkoxysilane beforecombining with organosilane and fluorosilane.
 20. The method of claim17, wherein the siloxane polymer solution is prepared in a two-stepprocess comprising preparing the hydrolyzed alkoxysilane beforecombining with organosilane.
 21. The method of claim 17, wherein thecoating is thermally cured at 120° C. to 700° C.
 22. The method of claim17, wherein the coating has a thickness of 80 nm to 500 nm after curing.23. The method of claim 17, wherein the glass substrate is at least oneof a window, an architectural glass, an LED, a semi-conductor, anexposed photovoltaic element, a lens, a diffuser, a mirror, awindshield, an automotive glass, a screen, a display, goggles,eyeglasses, sunglasses, a greenhouse glass, a hybrid solar surface, amarine glass, an aviation glass, a glass used in transportation, and amobile device screen.
 24. A coating comprising a dried gel preparedfrom: (i) a siloxane polymer A formed from an acid hydrolyzedalkoxysilane, an acid hydrolyzed organosilane, and optionally an acidhydrolyzed organofluorosilane, wherein the hydrolyzed organosilane andthe optional hydrolyzed organofluorosilane are each separately preparedbefore combining with each other and with the acid hydrolyzedalkoxysilane or with another reagent, wherein the siloxane polymer A hasthe following formula:[RSi(OH)₂O_(0.5)]_(a)[RSiO_(1.5)]_(b)[RSi(OH)O]_(c)[R′Si(OH)₂O_(0.5)]_(m)[R′SiO_(1.5)]_(n)[R′Si(OH)O]_(p)[SiO2]_(w)[Si(OH)O_(1.5)]_(x)[Si(OH)₂O]_(y)[Si(OH)₃O_(0.5)]_(z),where R is selected from the group consisting of independently methyl oroptionally substituted or unsubstituted C2 to C 10 alkyl group, asubstituted or unsubstituted C3 to C20 cycloalkyl group, a substitutedor unsubstituted C1 to C 10 hydroxyalkyl group, a substituted orunsubstituted C6 to C20 aryl group, a substituted or unsubstituted C2 toC20 heteroaryl group, a substituted or unsubstituted C2 to C 10 alkenylgroup, a substituted or unsubstituted carboxyl group, a substituted orunsubstituted (meth)acryl group a substituted or unsubstitutedglycidylether group, or a combination thereof, R′ is selected from thegroup consisting of a fluorine substituted C3 alkyl group or optionallyC4 to C10 alkyl group, a fluorine substituted C3 to C20 cycloalkylgroup, a fluorine substituted C1 to C10 hydroxyalkyl group, a fluorinesubstituted aryl group, a fluorine substituted C2 to C20 heteroarylgroup, a fluorine substituted C2 to C10 alkenyl group, a fluorinesubstituted carboxyl group, a substituted or unsubstituted (meth)acrylgroup, a fluorine substituted glycidylether group, or a combinationthereof, 0<a,b,c,w,x,y,z<0.9, 0≦m,n,p<0.9, and a+b+c+m+n+p+w+x+y+z=1;the siloxane polymer composition further comprising a hydrolysis acidcatalyst; a polar organic solvent; and (ii) at least one additiveselected from the group consisting of: a porogen; a template; basicSi—OH condensation catalyst; and a surfactant.
 25. The coating of claim24, wherein the coating exhibits: an absolute reduction in reflection of1.0% to 3.5% as compared to uncoated glass; a thickness of 80 to 160 nm;and sufficient toughness, abrasion resistance and adhesion to glass topass standard EN-1096-2 with an absolute change in reflection of no morethan 0.5% as measured after 2,000 abrasion strokes.
 26. The coating ofclaim 24, wherein the coating improves the peak power output of thesolar module by 1.0% to 3.5% on a relative basis.
 27. The composition ofclaim 1, further comprising at least one of a nano-filler and anadhesion promoter.
 28. The method of claim 7, the siloxane polymercomposition further comprising at least one of a nano-filler and anadhesion promoter.